Rated 4 out of 5 stars
Appears to be partly incompatible with 23a2. Not all features working. Hoping to see update, this is a great add-on.This review is for a previous version of the add-on (2.1.1).
I test this add-on regularly on the latest build of Thunderbird (i.e. the Daily branch), and I haven't found any issues. If I've missed something, please file a bug: https://bitbucket.org/squib/mail-summaries/issues/new
EDIT: I'm not sure if you'll see this, but I noticed that you filed a bug (thanks!) and mentioned a picture, but I can't see a picture in the bug report.