This add-on adds arrow buttons at the top of the folder pane which rotate back and forth through the various available folder views
This add-on also causes Thunderbird to automatically switch to the "All Folders" view when you hover over the title above the folder tree for several seconds during a message drag & drop operation, and switch back automatically after the drop. In the add-on preferences, you can set the delay before the view is switched.
Finally, in the add-on preferences, you can select which views are accessible in the pop-up menu at the top of the folder list, and of those, which show up when you rotate through the views using the arrow buttons.
If you want to use this add-on with versions of Thunderbird prior to 49, you will need to download version 1.14. This older version does not have the ability to control which views are enabled.
This add-on is incompatible with the "Maximize Message Pane" add-on.