lhglenn said

Somehow I accidentally deleted a very important mailbox folder from my Thunderbird account. This mailbox had quite a few subfolders in it. I would very much like to retrieve it if that is possible.

Hi  !

Don't you just hate it when that happens  ! You could go download 'Apowersoft Data Recovery' if you're sure you've really deleted it. Best of luck !

Wish that would have worked, but it didn't.  :-(

I'm so sorry to hear that ....
But I'm sure that one of the experts here will give you some proper advice and help solve your problem  !
Best wishes and good luck   !!!