Review for Calendar Tweaks by Marcel Oosterbeek
Rated 5 out of 5 stars
I'm very sorry to see that this great add-on is no longer available due to an update of Thunderbird.
I've used it with pleasure for a long time.
As announced on the Calendar Tweaks home page some time ago, there will be no more development or updates for Calendar Tweaks.
To create your own collections, you must have a Mozilla Add-ons account.