diff --git a/nbdime/webapp/templates/compare.html b/nbdime/webapp/templates/compare.html
index d22bf65e..a6fcef0f 100644
--- a/nbdime/webapp/templates/compare.html
+++ b/nbdime/webapp/templates/compare.html
@@ -9,18 +9,18 @@ <h3>Notebook Diff/Merge</h3>
       <form id="nbdime-compare-form" class="nbdime-forms">
         <fieldset>
           <legend>Please input filenames of notebooks to compare:</legend>
-          <label>Local:</label>
-          <input id="compare-local" type="text" name="local" value="{{ config_data['local']|e }}" />
-          <label>Base:</label>
-          <input id="compare-base" type="text" name="base" value="{{ config_data['base']|e }}" />
-          <label>Remote:</label>
-          <input id="compare-remote" type="text" name="remote" value="{{ config_data['remote']|e }}" />
+          <label>Local:
+          <input id="compare-local" type="text" name="local" value="{{ config_data['local']|e }}" /></label>
+          <label>Base:
+          <input id="compare-base" type="text" name="base" value="{{ config_data['base']|e }}" /></label>
+          <label>Remote:
+          <input id="compare-remote" type="text" name="remote" value="{{ config_data['remote']|e }}" /></label>
           <input id="nbdime-run-compare" type="submit" name="auto" value="Compare files" />
           <button id="nbdime-download" style="display: none" type="button">Download</button>
         </fieldset>
       </form> <!-- nbdime-forms -->
       <div id="nbdime-header-buttonrow">
-        <input id="nbdime-hide-unchanged" type="checkbox"><label for="cbox1">Hide unchanged cells</label></input>
+        <label><input id="nbdime-hide-unchanged" type="checkbox"></input>Hide unchanged cells</label>
         <button id="nbdime-save" style="display: none">Save</button>
         <button id="nbdime-download" style="display: none">Download</button>
         <button id="nbdime-close" style="display: none">Close tool</button>
diff --git a/nbdime/webapp/templates/diff.html b/nbdime/webapp/templates/diff.html
index 7d16c40b..447675eb 100644
--- a/nbdime/webapp/templates/diff.html
+++ b/nbdime/webapp/templates/diff.html
@@ -9,15 +9,15 @@ <h3>Notebook Diff</h3>
       <form id="nbdime-diff-form" class="nbdime-forms">
         <fieldset>
           <legend>Please input filenames/URLs of notebooks to diff:</legend>
-          <label>Base:</label>
-          <input id="diff-base" type="text" name="base" value="{{ config_data['base']|e }}" />
-          <label>Remote:</label>
-          <input id="diff-remote" type="text" name="remote" value="{{ config_data['remote']|e }}" />
+          <label>Base:
+          <input id="diff-base" type="text" name="base" value="{{ config_data['base']|e }}" /></label>
+          <label>Remote:
+          <input id="diff-remote" type="text" name="remote" value="{{ config_data['remote']|e }}" /></label>
           <input id="nbdime-run-diff" type="submit" name="diff" value="Diff files" />
         </fieldset>
       </form> <!-- nbdime-forms -->
       <div id="nbdime-header-buttonrow">
-        <input id="nbdime-hide-unchanged" type="checkbox"><label for="cbox1">Hide unchanged cells</label></input>
+        <label><input id="nbdime-hide-unchanged" type="checkbox"></input>Hide unchanged cells</label>
         <button id="nbdime-trust" style="display: none">Trust outputs</button>
         <button id="nbdime-close" type="checkbox" style="display: none">Close tool</button>
         <button id="nbdime-export" type="checkbox" style="display: none">Export diff</button>
diff --git a/nbdime/webapp/templates/difftool.html b/nbdime/webapp/templates/difftool.html
index ff7a5f11..5c86959d 100644
--- a/nbdime/webapp/templates/difftool.html
+++ b/nbdime/webapp/templates/difftool.html
@@ -5,7 +5,7 @@
     <div id="nbdime-header" class="nbdime-Diff">
       <h3>Notebook Diff</h3>
       <div id="nbdime-header-buttonrow">
-        <input id="nbdime-hide-unchanged" type="checkbox"><label for="cbox1">Hide unchanged cells</label></input>
+        <label><input id="nbdime-hide-unchanged" type="checkbox"></input>Hide unchanged cells</label>
         <button id="nbdime-trust" style="display: none">Trust outputs</button>
         <button id="nbdime-close" style="display: none">Close tool</button>
         <button id="nbdime-export" style="display: none">Export diff</button>
diff --git a/nbdime/webapp/templates/merge.html b/nbdime/webapp/templates/merge.html
index 9de50977..a8e7ce00 100644
--- a/nbdime/webapp/templates/merge.html
+++ b/nbdime/webapp/templates/merge.html
@@ -9,18 +9,18 @@ <h3>Notebook Merge</h3>
       <form id="nbdime-merge-form" class="nbdime-forms">
         <fieldset>
           <legend>Please input filenames/URLs of notebooks to merge:</legend>
-          <label>Local:</label>
-          <input id="merge-local" type="text" name="local" value="{{ config_data['local']|e }}" />
-          <label>Base:</label>
-          <input id="merge-base" type="text" name="base" value="{{ config_data['base']|e }}" />
-          <label>Remote:</label>
-          <input id="merge-remote" type="text" name="remote" value="{{ config_data['remote']|e }}" />
+          <label>Local:
+          <input id="merge-local" type="text" name="local" value="{{ config_data['local']|e }}" /></label>
+          <label>Base:
+          <input id="merge-base" type="text" name="base" value="{{ config_data['base']|e }}" /></label>
+          <label>Remote:
+          <input id="merge-remote" type="text" name="remote" value="{{ config_data['remote']|e }}" /></label>
           <input id="nbdime-run-merge" type="submit" name="merge" value="Merge files" />
           <button id="nbdime-download" style="display: none" type="button">Download</button>
         </fieldset>
       </form> <!-- nbdime-forms -->
       <div id="nbdime-header-buttonrow">
-        <input id="nbdime-hide-unchanged" type="checkbox"><label for="cbox1">Hide unchanged cells</label></input>
+        <label><input id="nbdime-hide-unchanged" type="checkbox"></input>Hide unchanged cells</label>
         <button id="nbdime-save" style="display: none">Save</button>
         <button id="nbdime-download" style="display: none">Download</button>
         <button id="nbdime-close" style="display: none">Close tool</button>
diff --git a/nbdime/webapp/templates/mergetool.html b/nbdime/webapp/templates/mergetool.html
index 7820add4..bfe62d76 100644
--- a/nbdime/webapp/templates/mergetool.html
+++ b/nbdime/webapp/templates/mergetool.html
@@ -5,7 +5,7 @@
     <div id="nbdime-header" class="nbdime-Merge">
       <h3>Notebook Merge</h3>
       <div id="nbdime-header-buttonrow">
-        <input id="nbdime-hide-unchanged" type="checkbox"><label for="cbox1">Hide unchanged cells</label></input>
+        <label><input id="nbdime-hide-unchanged" type="checkbox"></input>Hide unchanged cells</label>
         <button id="nbdime-save" style="display: none">Save</button>
         <button id="nbdime-download" style="display: none">Download</button>
         <button id="nbdime-close" style="display: none">Close tool</button>
diff --git a/packages/nbdime/src/common/mergeview.ts b/packages/nbdime/src/common/mergeview.ts
index 808f3309..e2f83144 100644
--- a/packages/nbdime/src/common/mergeview.ts
+++ b/packages/nbdime/src/common/mergeview.ts
@@ -1196,7 +1196,7 @@ function getMatchingEditLineLC(toMatch: Chunk, chunks: Chunk[]): number {
     }
   }
   // toMatch is not in chunks list, add lines delta from the last chunk
-  return toMatch.baseTo + (previous ? (previous.remoteTo - previous.baseTo) : 0);
+  return toMatch.baseTo + (previous ? previous.remoteTo - previous.baseTo : 0);
 }
 
 /**
@@ -1444,7 +1444,13 @@ export class MergeView extends Panel {
     const additionalExtensions = inMergeView
       ? [listener, mergeControlGutter, getCommonEditorExtensions(inMergeView)]
       : getCommonEditorExtensions(inMergeView);
-    if (this._collapseIdentical >= 0) {
+    const singlePane = !merged && (remote?.unchanged || remote?.added || remote?.deleted)
+    if (
+      // no collapse
+      this._collapseIdentical >= 0 &&
+      // not displaying a single editor
+      !singlePane
+    ) {
       additionalExtensions.push(CollapsedRangesField);
     }
 
@@ -1686,7 +1692,7 @@ export class MergeView extends Panel {
             Decoration.widget({
               widget: new PaddingWidget(delta * lineHeight),
               block: true,
-                side: -1,
+              side: -1,
             }),
           );
         }
diff --git a/ui-tests/data/merge_test6/center.ipynb b/ui-tests/data/merge_test6/center.ipynb
new file mode 100644
index 00000000..7a13ad78
--- /dev/null
+++ b/ui-tests/data/merge_test6/center.ipynb
@@ -0,0 +1,78 @@
+{
+    "cells": [
+        {
+            "cell_type": "markdown",
+            "id": "b84ee5a1",
+            "metadata": {},
+            "source": [
+                "# Initial notebook"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": 1,
+            "id": "a29ef27d",
+            "metadata": {},
+            "outputs": [
+                {
+                    "data": {
+                        "text/plain": [
+                            "'hello the world'"
+                        ]
+                    },
+                    "execution_count": 1,
+                    "metadata": {},
+                    "output_type": "execute_result"
+                }
+            ],
+            "source": [
+                "# This is the first cell in the initial commit\n",
+                "a = \"hello the world\"\n",
+                "a"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": 2,
+            "id": "0b24d979",
+            "metadata": {},
+            "outputs": [
+                {
+                    "data": {
+                        "text/plain": [
+                            "'hello Tony Stark'"
+                        ]
+                    },
+                    "execution_count": 2,
+                    "metadata": {},
+                    "output_type": "execute_result"
+                }
+            ],
+            "source": [
+                "# This is the last cell in the initial commit\n",
+                "a.replace(\"the world\", \"Tony Stark\")"
+            ]
+        }
+    ],
+    "metadata": {
+        "kernelspec": {
+            "display_name": "Python 3",
+            "language": "python",
+            "name": "python3"
+        },
+        "language_info": {
+            "codemirror_mode": {
+                "name": "ipython",
+                "version": 3
+            },
+            "file_extension": ".py",
+            "mimetype": "text/x-python",
+            "name": "python",
+            "nbconvert_exporter": "python",
+            "pygments_lexer": "ipython3",
+            "version": "3.9.5"
+        }
+    },
+    "nbformat": 4,
+    "nbformat_minor": 5
+}
\ No newline at end of file
diff --git a/ui-tests/data/merge_test6/left.ipynb b/ui-tests/data/merge_test6/left.ipynb
new file mode 100644
index 00000000..49d99454
--- /dev/null
+++ b/ui-tests/data/merge_test6/left.ipynb
@@ -0,0 +1,101 @@
+{
+    "cells": [
+        {
+            "cell_type": "markdown",
+            "id": "b84ee5a1",
+            "metadata": {},
+            "source": [
+                "# a-branch notebook"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": 1,
+            "id": "a29ef27d",
+            "metadata": {},
+            "outputs": [
+                {
+                    "data": {
+                        "text/plain": [
+                            "'hello the world'"
+                        ]
+                    },
+                    "execution_count": 1,
+                    "metadata": {},
+                    "output_type": "execute_result"
+                }
+            ],
+            "source": [
+                "# This is the first cell in the initial commit\n",
+                "a = \"hello the world\"\n",
+                "a"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": 2,
+            "id": "a29bf27d",
+            "metadata": {},
+            "outputs": [
+                {
+                    "data": {
+                        "text/plain": [
+                            "'The answer is 42'"
+                        ]
+                    },
+                    "execution_count": 2,
+                    "metadata": {},
+                    "output_type": "execute_result"
+                }
+            ],
+            "source": [
+                "# This is a new cell in a-branch\n",
+                "b = \"The answer is 42\"\n",
+                "b"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": 3,
+            "id": "0b24d979",
+            "metadata": {},
+            "outputs": [
+                {
+                    "data": {
+                        "text/plain": [
+                            "'hello a-branch'"
+                        ]
+                    },
+                    "execution_count": 3,
+                    "metadata": {},
+                    "output_type": "execute_result"
+                }
+            ],
+            "source": [
+                "# This is the last cell in the initial commit\n",
+                "a.replace(\"the world\", \"a-branch\")"
+            ]
+        }
+    ],
+    "metadata": {
+        "kernelspec": {
+            "display_name": "Python 3",
+            "language": "python",
+            "name": "python3"
+        },
+        "language_info": {
+            "codemirror_mode": {
+                "name": "ipython",
+                "version": 3
+            },
+            "file_extension": ".py",
+            "mimetype": "text/x-python",
+            "name": "python",
+            "nbconvert_exporter": "python",
+            "pygments_lexer": "ipython3",
+            "version": "3.9.5"
+        }
+    },
+    "nbformat": 4,
+    "nbformat_minor": 5
+}
\ No newline at end of file
diff --git a/ui-tests/data/merge_test6/right.ipynb b/ui-tests/data/merge_test6/right.ipynb
new file mode 100644
index 00000000..905dcc0b
--- /dev/null
+++ b/ui-tests/data/merge_test6/right.ipynb
@@ -0,0 +1,100 @@
+{
+    "cells": [
+        {
+            "cell_type": "markdown",
+            "id": "b84ee5a1",
+            "metadata": {},
+            "source": [
+                "# Enhanced notebook"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": 1,
+            "id": "a29ef27d",
+            "metadata": {},
+            "outputs": [
+                {
+                    "data": {
+                        "text/plain": [
+                            "'hello the world'"
+                        ]
+                    },
+                    "execution_count": 1,
+                    "metadata": {},
+                    "output_type": "execute_result"
+                }
+            ],
+            "source": [
+                "# This is the first cell in the initial commit\n",
+                "a = \"hello the world\"\n",
+                "a"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": 2,
+            "id": "0b24d979",
+            "metadata": {},
+            "outputs": [
+                {
+                    "data": {
+                        "text/plain": [
+                            "'hello Superman'"
+                        ]
+                    },
+                    "execution_count": 2,
+                    "metadata": {},
+                    "output_type": "execute_result"
+                }
+            ],
+            "source": [
+                "# This is the last cell in the initial commit\n",
+                "a.replace(\"the world\", \"Superman\")"
+            ]
+        },
+        {
+            "cell_type": "code",
+            "execution_count": 3,
+            "id": "0b74d979",
+            "metadata": {},
+            "outputs": [
+                {
+                    "data": {
+                        "text/plain": [
+                            "'What about Batman?'"
+                        ]
+                    },
+                    "execution_count": 3,
+                    "metadata": {},
+                    "output_type": "execute_result"
+                }
+            ],
+            "source": [
+                "# This the new last cell on master\n",
+                "print(\"What about Batman?\")"
+            ]
+        }
+    ],
+    "metadata": {
+        "kernelspec": {
+            "display_name": "Python 3",
+            "language": "python",
+            "name": "python3"
+        },
+        "language_info": {
+            "codemirror_mode": {
+                "name": "ipython",
+                "version": 3
+            },
+            "file_extension": ".py",
+            "mimetype": "text/x-python",
+            "name": "python",
+            "nbconvert_exporter": "python",
+            "pygments_lexer": "ipython3",
+            "version": "3.9.5"
+        }
+    },
+    "nbformat": 4,
+    "nbformat_minor": 5
+}
\ No newline at end of file
diff --git a/ui-tests/package-lock.json b/ui-tests/package-lock.json
index 9d389c9b..827e33f3 100644
--- a/ui-tests/package-lock.json
+++ b/ui-tests/package-lock.json
@@ -40,6 +40,7 @@
       "version": "2.3.2",
       "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.2.tgz",
       "integrity": "sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==",
+      "dev": true,
       "hasInstallScript": true,
       "optional": true,
       "os": [
@@ -49,23 +50,6 @@
         "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
       }
     },
-    "node_modules/playwright": {
-      "version": "1.38.1",
-      "resolved": "https://registry.npmjs.org/playwright/-/playwright-1.38.1.tgz",
-      "integrity": "sha512-oRMSJmZrOu1FP5iu3UrCx8JEFRIMxLDM0c/3o4bpzU5Tz97BypefWf7TuTNPWeCe279TPal5RtPPZ+9lW/Qkow==",
-      "dependencies": {
-        "playwright-core": "1.38.1"
-      },
-      "bin": {
-        "playwright": "cli.js"
-      },
-      "engines": {
-        "node": ">=16"
-      },
-      "optionalDependencies": {
-        "fsevents": "2.3.2"
-      }
-    },
     "node_modules/playwright-core": {
       "version": "1.36.2",
       "resolved": "https://registry.npmjs.org/playwright-core/-/playwright-core-1.36.2.tgz",
@@ -77,17 +61,6 @@
       "engines": {
         "node": ">=16"
       }
-    },
-    "node_modules/playwright/node_modules/playwright-core": {
-      "version": "1.38.1",
-      "resolved": "https://registry.npmjs.org/playwright-core/-/playwright-core-1.38.1.tgz",
-      "integrity": "sha512-tQqNFUKa3OfMf4b2jQ7aGLB8o9bS3bOY0yMEtldtC2+spf8QXG9zvXLTXUeRsoNuxEYMgLYR+NXfAa1rjKRcrg==",
-      "bin": {
-        "playwright-core": "cli.js"
-      },
-      "engines": {
-        "node": ">=16"
-      }
     }
   }
 }
diff --git a/ui-tests/tests/nbdime-merge-test6.spec.ts b/ui-tests/tests/nbdime-merge-test6.spec.ts
new file mode 100644
index 00000000..28a41bfe
--- /dev/null
+++ b/ui-tests/tests/nbdime-merge-test6.spec.ts
@@ -0,0 +1,18 @@
+import { expect, test } from '@playwright/test';
+
+test.describe('merge test6', () => {
+  test.beforeEach(async ({ page }) => {
+    await page.goto('http://localhost:41000/merge');
+    await page.locator('#merge-local').fill('data/merge_test6/left.ipynb');
+    await page.locator('#merge-base').fill('data/merge_test6/center.ipynb');
+    await page.locator('#merge-remote').fill('data/merge_test6/right.ipynb');
+    await page.getByRole('button', { name: 'Merge files' }).click();
+  });
+
+  test('take a snapshot at opening', async ({ page }) => {
+    await page.getByText('Hide unchanged cells').click()
+    await page.getByText('a = "hello the world"').waitFor();
+    // Check that single editor are not collapsed; added cell and unchanged cell
+    expect.soft(await page.locator('#main').screenshot()).toMatchSnapshot();
+  });
+});
diff --git a/ui-tests/tests/nbdime-merge-test6.spec.ts-snapshots/merge-test6-take-a-snapshot-at-opening-1-linux.png b/ui-tests/tests/nbdime-merge-test6.spec.ts-snapshots/merge-test6-take-a-snapshot-at-opening-1-linux.png
new file mode 100644
index 00000000..2f3bcd34
Binary files /dev/null and b/ui-tests/tests/nbdime-merge-test6.spec.ts-snapshots/merge-test6-take-a-snapshot-at-opening-1-linux.png differ
diff --git a/ui-tests/tests/nbdime-merge-test6.spec.ts-snapshots/merge-test6-take-a-snapshot-at-opening-1-win32.png b/ui-tests/tests/nbdime-merge-test6.spec.ts-snapshots/merge-test6-take-a-snapshot-at-opening-1-win32.png
new file mode 100644
index 00000000..f780199e
Binary files /dev/null and b/ui-tests/tests/nbdime-merge-test6.spec.ts-snapshots/merge-test6-take-a-snapshot-at-opening-1-win32.png differ