Developer reply by kkapsner
Rated 3 out of 5 stars
The extension works when the KeePassXC database is unlocked, but whenever Thunderbird refreshes an account and the database is locked, it will open a new browser page asking for OAuth2 confirmation for each account.
As the access tokens for oauth are stored in the KeePassXC database Thunderbird has no way to know these when the database is locked. This behaviour is intended and a security feature.
To create your own collections, you must have a Mozilla Add-ons account.