Review for SortPref by Stuart Halliday
Rated 4 out of 5 stars
Works well in TB 3.1 once I tweaked the version limitation and is a much needed feature as I have 50+ folders and to have to sort them manually one by one is incredibly irritating without your add-on.
But I still have to sort by threaded view, so if you could be so kind and add a threaded/non-threaded switch as well that would be great.
To create your own collections, you must have a Mozilla Add-ons account.