Developer reply by Arnaud Abelard
Rated 5 out of 5 stars
Will miss it; any chance of updating for TB v60+?
https://wiki.mozilla.org/Thunderbird/Add-ons_Guide_57
There's a new version coming up which just adds support for tb 60+. It's awaiting review by the Thunderbird dev team.
To create your own collections, you must have a Mozilla Add-ons account.