Similar issue here, but mine is going even further. Folder order is changing by itself. What was previously in alphabetical order is now all mixed up.

In recent monthly release versions, you can right click on the account name "Local folders" and select "Reset Folder Order". It will alphabetize the top-level folders.

I do not know why your folders fell out of sequence or if it will happen again.

I have version 145 and it indicates that I am up to date on the recent releases. I did right click on that folder, but it did not give me that option to reset the order. Which version do you have? I am suppose to be receiving all of recent versions.

The option is in 145. Did you click on a folder or on the account name? Click on the account name "Local Folders".

If you don't see it, I am guessing that an add-on is interfering with folder order and this menu. Try running Thunderbird in troubleshooting mode and see if the problems persist. Help menu > Troubleshoot mode.

As a novice to the complexity of Thunderbird (I really am best described a just an end-user), I misstated the problem. I did find the proper "LOCAL FOLDERS" folder. When I did a right click on that, I did find the "Reset Folder Order." My problem is that I have a sub-folder under that is also called "Local Folders." THAT is the folder that I want to re-alphabetize. I want to reset the order of those sub-folders. A right click on that "local folders" folder (which is really a sub-folder) does not give me an option to reorganize the order. Sorry for my lack of understanding the geography of the system.

No need to apologize. Most of us here are just users.

The action operates only on the top level of folders. Maybe you could move folders to the top level if you have two (redundant?) levels of local folders?

Thanks for the suggestion. I will be it a try at a later time.