Instructing Thunderbird to arrange Sub-Folders in Inbox back into alphabetical order

Have been using Thunderbird and Firefox for decades, naturally, and have several email accounts. Within each account, I'm a prolific user of folders within the respective Inboxes. For years, these folders have remained in Alphabetical Order, as when they were set up. Recently, however, for no reason that I can suss, the sub-folders in the Inbox of one of my accounts have been gone "all agley", ie. they're listed all higgledy-piggledy in random order. This isn't a problem for my message filter - but it's a real problem for me, having to scan down a very long, disorganised list to find any particular folder I want to open. I've searched for an instruction to instruct Thunderbird to arrange the Folders in my Inbox in Alphabetical Order and can't find anything. Can anyone help me, please. Many thanks in anticipation to all you helpful Thunderbird Users and Contributors. Cathleen (London, UK)