Review for Folder Pane View Switcher by Hulibobu
Rated 5 out of 5 stars
I suggest using this together with the "Advanced Unread Folders" add-on. That one adds a very useful sorting function that can be used with this one.
This review is for a previous version of the add-on (1.7).To create your own collections, you must have a Mozilla Add-ons account.