Rated 5 out of 5 stars

Does exactly what I need. This should be standard in Firefox.

Did not find problems in normal use. But I did not test everything that might be possible.

If I could assign shortcut keys so that I can jump directly to a certain group this would be great.

The keys ctrl + ` in Firefox itself is very poor since you just can go from one group to the next or with shift plus the keys above back again.