This is now supported natively

[krinoid]

Thanks for providing this fix! Just FYI, FF introduced recently insertAfterCurrentExceptPinned config in about:config (after 14 years: https://bugzilla.mozilla.org/show_bug.cgi?id=655445), so one just needs to enable that. Tested on my machine, works as expected.

[xeruf]

Thanks so much! I just came here cause it seemed it stopped working - this is great news, one extension less to fix features ;)