The website article editor currently looks like this:

When Side-by-Side or Fullscreen is toggled, the sitewide header covers the toolbar, making it impossible to revert to regular editing by mouse or access any of the buttons on the toolbar.

Only tested on the latest Firefox on Linux, as I don't have current access to other browsers or operating systems.
The website article editor currently looks like this:

When Side-by-Side or Fullscreen is toggled, the sitewide header covers the toolbar, making it impossible to revert to regular editing by mouse or access any of the buttons on the toolbar.
Only tested on the latest Firefox on Linux, as I don't have current access to other browsers or operating systems.