Developer reply by dreadnaut
Rated 1 out of 5 stars
No point in listing an extension as compatible if it no longer works, surely?
This review is for a previous version of the add-on (1.4.0).That's way the listing says "Works with Thunderbird 68.0 - 73.0". Plus, the large warning in the description.
I'm working on getting this to work on TB78+, but I have to wait for some changes on the Thunderbird side.
To create your own collections, you must have a Mozilla Add-ons account.