I strongly second this. I have a large number of operations in my Thunderbird Activity Manager window which for weeks have failed to ever complete.
Specifically it's a deleted folders bug in thunderbird when dealing with both IMAP servers at my 2 mail hosts (work and private). The folders were deleted a week ago without issue, but Thunderbird just will not stop trying and failing and retrying. Activity Manager messages:
The attempted action (masked for privacy): "Deleted folder Sys-B-Tel /n z***@***.com"
Followed a short while later by this logic bending message: "The current operation on 'Sys-B-Tel' did not succeed. The mail server for account z***@***.com responded: Mailbox does not exist."
It's painfully bad. I get it, bugs happen. But please give us a way to abort recurring thunderbird actions that are failing for some dumb reason. They seem to be hidden somewhere users can't reach...
But @ZebulonGlitch I also suggest that, given that you have already traced the origins of your specific problem, to create an issue for it on Bugzilla.