Review for Checkbox Column by alta88
Rated 5 out of 5 stars
This addon has inspired select functionality to be added to core Thunderbird in v70+. Pick column Select Messages from the columnpicker.
Also included is 'no unwanted selection', meaning unselect in the column will prevent selecting anything in that folder on junk or delete or other message move actions.
To create your own collections, you must have a Mozilla Add-ons account.