Description

We currently have ways to programatically opt out of the Widgets editor but there is no user facing feature. While themes and plugins can simply remove_theme_support('widgets-block-editor') but a user has no setting to turn off.

I suggest we add a setting-less plugin that when activated acts as if the theme support is removed. So, if a user needs for instance an incompatible plugin (providing essential widgets that do not work in the new block editor) they can simply install this plugin and activate it for everything to be back to "normal".

Activating this plugin should restore:

• the Appearance > Widgets link should go to the legacy widgets editor
• the top bar [Site Name] > Widgets link should go to the legacy widgets editor
• the Appearance > Customize > Widgets should show the legacy Widgets section in the Customizer
• the Dashboard > Manage widgets should go to the legacy widgets editor.

Deactivating the plugin restores the default block based Widgets editor.

This plugin should be developed in its own repository.