registerPlugin is not working in Site editor

[wpsoul]

Description

When using function to register custom plugin for Sidebar, it doesn't work inside Site Editor environment (but works for post edit)

https://developer.wordpress.org/block-editor/how-to-guides/plugin-sidebar-0/

Also, when using Site editor, there is no back button, so, it's impossible to leave Editor and return to dashboard.

Step-by-step reproduction instructions

1. Register sidebar with registerPlugin or use any plugin which supports this options (I tried Greenshift, Qubely, Stackable)
2. Edit post - editor has custom plugin
3. Go to Appearance - Editor. No custom plugins are available in sidebar

Screenshots, screen recording, code snippet

No response

Environment info

No response

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

[leeshadle]

I'm seeing the same thing, a registered plugin sidebar works everywhere but the 'Site Editor'.

[awps]

No matter what I do, followed all the docs for registerPlugin, and it works everywhere except the Site Editor.

[vladolaru]

Ping!

[t-hamano]

For example, if you want to use PluginSidebar in the site editor, you need to load from another package, as shown below:

( function ( wp ) {
	...
    var PluginSidebar = wp.editSite.PluginSidebar;
	...
} )( window.wp );

In addition, change the dependencies for enqueuing javascript as follows:

wp_register_script(
    'plugin-sidebar-js',
    plugins_url( 'plugin-sidebar.js', __FILE__ ),
    array( 'wp-plugins', 'wp-edit-site', 'wp-element' ) // change dependencies
);

However, this is not mentioned in the documentation and may be confusing to developers, so it might be worth considering to update the documentation.