Rated 5 out of 5 stars
Very usefull when you have a lot of folders. Very well integrated in the thunderbird UI. Nice job.
One suggestion : in my case, I have a lot of archived folder and these ones appear in the extension's window. An option to show (or not) folders under 'Archive' root folder could be useful.
One last dream : moving a message directly in the same folder that the corresponding thread.