I was looking exactly for an addon which enables tab grouping only via Containers. That's why I used the addon "Conex" before, which isn't developed anymore since 4 years and is buggy. Thanks so much for this addon. It's the perfect replacement for Conex.

It feels and works like a clone of the tab grouping feature Chrome is using. Your addon is minimalistic but feature-rich.

Please keep it up, awesome work!