Which is your Thunderbird version?

147.0

Have you tried a R-click on the account folder > Reset Folder Order?

That option is only available for a folder and not a sub-folder. Unfortunately, I am trying to reset the "folder" order in a sub-folder. I can R-click a folder higher up in system and it will give me that option. Somehow, years ago, my series of "folders" was put in a sub-folder, but well organized (alphabetized). However, when I moved this to a new PC, I have two sets of folders in this sub-folder. Each are alphabetized in two sets. I want to combine the two sets in one big alphabetized set.

That option is only available for a folder and not a sub-folder.

It works for me > se my new screenshots!

I want to combine the two sets in one big alphabetized set.

Move the contents of the second subfolder to th first subfolder, then click on the account folder > Reset Folder Order

This time it did work. Great!! Thanks.