Rated 5 out of 5 stars

Does what it says it does.

For those folks who are having trouble finding the "tools" menu: its *not* the hamburger menu; its the old "tools" menu in the window header.

To get it to show (on windows) press and release the Alt key in Thunderbird; the top level File / Edit / View / etc bar will show at the top of the window. You want Tools -> Manually Sort Folders.