Selecting parents: Try clickthrough.

Clickthrough has you select the parent before you can select the child. This is already in place on the mobile breakpoints, this just expands it to desktop as well.

It is a work in progress, right now it is not working as intended: once you have "unlocked" the deepest level, it becomes immediately locked and you have to click through the layers again to unlock it again. The deepest layer should always be unlocked until you deselect all blocks again.

packages/block-editor/src/components/inner-blocks/index.js

@@ -106,14 +106,13 @@ class InnerBlocks extends Component {
 	render() {
 		const {
 			clientId,
-			isSmallScreen,
 			isSelectedBlockInRoot,
 			renderAppender,
 		} = this.props;
 		const { templateInProcess } = this.state;
 
 		const classes = classnames( 'editor-inner-blocks block-editor-inner-blocks', {
-			'has-overlay': isSmallScreen && ! isSelectedBlockInRoot,
+			'has-overlay': ! isSelectedBlockInRoot,
 		} );
 
 		return (

packages/block-library/src/columns/editor.scss

@@ -164,17 +164,5 @@ div.block-core-columns.is-vertically-aligned-bottom {
  */
 [data-type="core/column"] > .editor-block-list__block-edit > .editor-block-list__breadcrumb {
 	right: 0;
-}
-
-// The empty state of a columns block has the default appenders.
-// Since those appenders are not blocks, the parent, actual block, appears "hovered" when hovering the appenders.
-// Because the column shouldn't be hovered as part of this temporary passthrough, we unset the hover style.
-.wp-block-columns [data-type="core/column"].is-hovered {
-	> .block-editor-block-list__block-edit::before {
-		content: none;
-	}
-
-	.block-editor-block-list__breadcrumb {
-		display: none;
-	}
+	left: auto;
 }