No there is not one worth the effort is what I would say at the moment for your version. There is an addon that can do it. https://addons.thunderbird.net/en-US/thunderbird/addon/manually-sort-folders/ However V91 has been released and updates will commence in the next couple of weeks. The new version supports folder (or at least account) sorting natively. So you might want to just hold off and see if the new version does what you want.