Review for Provider for Google Calendar by Hamsterkind
Rated 4 out of 5 stars
4 stars instead of 5, because with thunderbird's latest release you need to deactivate and then reactivate the addon to make it work (I really hope it's a temporary bug you can fix ;) )
This review is for a previous version of the add-on (78.0.1).To create your own collections, you must have a Mozilla Add-ons account.