The version of that add-on for 68 doesn't let you move the Local Folders account like you could before because it no longer lets you select "Local Folders" as an account. Unfortunately the prior version of that add-on only supports up to version 64. The authors support page has an issue - https://github.com/protz/Manually-Sort-Folders/issues/101 submitted about that. The mail.accountmanager.accounts setting (in the config editor) lists the account ids for each account, each separated by a comma. At one time you could hack the account order by changing the order of the accounts in that setting. That doesn't seem to work anymore. https://protzenko.fr/jonathan/manually-sort-folders/ has unreleased builds of that add-on. I tried the latest one and it has the same restriction as the add-on on thunderbird.net. https://bugzilla.mozilla.org/show_bug.cgi?id=318467 is a bug report requesting the ability to change the sort order be included in Thunderbird, and has links to numerous duplicate bug reports. There has been discussion on the tb-planning mailing list that the features of this add-on should be included in Thunderbird but there doesn't seem to be a commitment to do that yet. So in the interim I think you need to wait and see if either the original author releases a new version that fixes the problem or the add-on becomes part of the "core" (Thunderbird).

Wow that bug report was opened and remains open 14 years later. I hope there is an Add-on solution. I miss my LF on top.