Review for Toggle Folderpane View by vrillusions
Rated 5 out of 5 stars
Was looking for a way to manage all the many folders I have and was annoyed that you could mark a folder as a favorite but to actually show that view required a lot of clicking. Now it's just a single button I can click to switch between the two views. This is now the second extension in thunderbird (enigmail was first). Maybe in a few years I'll find another one...
BTW for those that may have trouble finding it. It's not added to your toolbar by default so you have to right click on toolbar and choose customize and you'll see it at the bottom of the list.
To create your own collections, you must have a Mozilla Add-ons account.