Rated 5 out of 5 stars

I am very glad that this add-on was ported to the 78 Thunderbird. I organize my emails by correspondents, and over the years they have add up. Just clicking the right arrow to view only the new, unread messages is great. Thunderbird itself has a dropdown box to do so, but Folder Pane Switcher is much, much easier to use. Very recommended!