Rated 5 out of 5 stars
This is an absolutely must have brilliant add-on. Unfortunately since updating to the latest version of Thunderbird (52.0.1), the Arrows to control which Folder Pane is viewed have disappeared.This review is for a previous version of the add-on (1.11).
UPDATE: The arrows are back in this beta release:
Give it a try!
Please read "About this Add-on" at https://addons.mozilla.org/en-US/thunderbird/addon/folder-pane-view-switcher/.