Q Light Controller+

do you know if is it possible to modify a group?
I have't found a way to add a fixture once a group is created, similar problem to remove a fixture:
it's possible with the "minus" button but then the fixture is unpatched from the universe as well.

Now it's possible to rename a group but not to modify it.
Fixture Groups/Inspect:
I can only remove a fixture from the grid and the group selection get updated, nevertheless the removed fixture is still listed in the group.