the "recent destinations" list has shortened. I move incoming messages into other folders more often than this feature now allows, making more work for me to find that folder manually.

I don't use that feature much but I can see how that would be an improvement.

Ideas and suggestions can be made here:

https://connect.mozilla.org/t5/ideas/idb-p/ideas/label-name/thunderbird

What?? An improvement? Not for me. I see that there are tech-savvy ways to modify that list and its hard-coded limit (last 31 days), but I don't have that level of expertise. I regularly move incoming messages (unless I delete them after reading) to a dozen different subfolders or more, easily 8-10 a day. Is there a step-by-step instruction for changing this list that a non-expert can follow? Thanks.

No, there is not.

If you would like the current limit to be changed you should make the suggestion where I mentioned above.

If you consider this to be a bug, you can report it here:

https://bugzilla.mozilla.org/describecomponents.cgi?product=Thunderbird

Thanks, Lin. I have posted a query in "Ideas" I do not think it's a bug; it's likely most people don't use this feature like I do, and maybe a short list saves space elsewhere in the system. But if I can adapt it to my needs, so much the better. Thanks again.

From "New In Thunderbird Desktop" -

   Recent Destinations in General Settings now supports alphabetical sorting. 

See: Thunderbird app menu ☰ > Settings > General > Scroll down to Sort order: under Folder Management Options and choose Alphabetical or Most recent.

Current versions of TB have a setting: General:Folder Management Options: Recent Destinations option to change sort and number. Thanks.