Site Editor: Top Toolbar 'Add New Template' missing for mobile

[colorful-tones]

Description

There is no means to Add a New Template in the Site Editor for small screens. I discovered this while debugging #49772

Step-by-step reproduction instructions

1. Launch the Site Editor by visiting Appearance > Editor
2. Click 'Templates' to view available templates
3. Note the missing + icon where you would click to 'Add New Template' on mobile, which should appear next to the top heading of 'Templates'

Screenshots, screen recording, code snippet

desktop	mobile

Environment info

• WordPress 6.3 / TT3 theme
• Gutenberg Trunk only activated
• Any screensize under 400 (for what I tested) using Chrome Dev Tools and Toggle Device Toolbar

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[colorful-tones]

I believe the code where this is happening is:

gutenberg/packages/edit-site/src/components/sidebar-navigation-screen-templates/index.js

Lines 47 to 61 in 7282cf6

	const canCreate = ! isMobileViewport;
	return (
	<SidebarNavigationScreen
	title={ __( 'Templates' ) }
	description={ __(
	'Express the layout of your site with templates'
	) }
	actions={
	canCreate && (
	<AddNewTemplate
	templateType={ 'wp_template' }
	toggleProps={ {
	as: SidebarButton,
	} }
	/>

[t-hamano]

I think this issue is related to #49769.

[colorful-tones]

@t-hamano thanks for the duplicate note. I agree, but I made a note for Anne to update her original Issue notes, because there is nothing that references or notes that the Add a New Template button is missing. It is on the same screen that is being reported in Anne's Issue, but in a different spot and could easily be missed when that Issue is addressed. Once she updates with that note then I'll be sure to close this out. Thanks!