Meanwhile it'll happy trim the sender and subject fields to 3 chars each (BY DEFAULT).
The real problem is the list of email in this folder isn't above the email pane, it's to the side eating horizontal space. I think I want "compact view", but it's greyed out.
The first google hit for "thunderbird compact view greyed out" is https://bugzilla.mozilla.org/show_bug.cgi?id=197434 closed TWENTY ONE YEARS AGO.
Why did the implement the ABILITY to grey it out? Why would it EVER be greyed out? What's the POINT of doing that?