Спасибо за хороший инструмент.
Почему-то в настройках группы не получается настроить захват регуляркой локальных документов по схеме URI file:///
Это вообще возможно?

That helps: (by rk)
EDIT. For those having similar issues. I think the trick is to open about:config and set closeWindowWithLastTab to false.

Simple and effective.

I tried more group tabs extensions, but this is the best solution for people who were using the old Tab groups manager which worked before Firefox Quantum. Many thanks!

Najlepsza!

Awesome add-on

Pretty great add-on, just wish I could open a group and have my currently open tabs merge into it.