Rated 4 out of 5 stars
It was very helpful when it worked. Unfortunately, Tbird 68.3.1 update broke it.
The account list is displayed, but the tabs and buttons are all missing. Zero functionality.
Let's hope the dev hasn't abandoned this project. I just converted my numerous accounts to IMAP, making re-sorting necessary. I start to do so and find this addon no longer works.
No joy. =(