Review for Flat Folder Tree (updated) by David Levin
Rated 5 out of 5 stars
This is a helpful, if not essential, navigation tool. If you have a large number of folders and sub-folders, finding a particular folder can be challenging. After years of using Thunderbird, my folder structure is extensive. Today, I could not find a sub-folder for a old project - drove me nuts. I searched add-ons and found this tool. Challenge solved. Kudos to the developer.
This review is for a previous version of the add-on (1.1.3).To create your own collections, you must have a Mozilla Add-ons account.