To try the thousands of add-ons available here, download Mozilla Firefox, a fast, free way to surf the Web!
CloseWelcome to Firefox Add-ons.
Choose from thousands of extra features and styles to make Firefox your own.
CloseReview for DeepDark for Thunderbird by Darkhoof
Rated 5 out of 5 stars
Finally the best Thunderbird theme is available for version 68. :D
I have a personal preference of increasing the spacing of the message row list. If you changed that yourself it would be awesome, but nothing that some userChrome.css tinkering doesn't fix anyway.
To create your own collections, you must have a Mozilla Add-ons account.