Review for Manually sort folders by David Marcinowski
Rated 5 out of 5 stars
Your add-on is still valuable in that gave the user the ability to choose a particular folder to always start up in, instead of having to start in the folder you were in when you shut Thunderbird down in if it wasn't your favoured startup folder.
Why the devs don't build this function in already is unfathomable but it isn't.
To create your own collections, you must have a Mozilla Add-ons account.