I think it’s possible because in Object menu -> Parent -> Object (ctrl P)
you can make a list of objects and with a loop, you can hide all this list.
hideObjects = 1
for obj in bpy.context.selected_objects:
obj.hide = hideObjects
Kubeczek77 don’t want speak “group” but “child” in outliner.
I mean it’s possible to hide all child of a hierarchie with a script but I don’t know an actual add-on to make this.
But about Group, it’s possible to hide all elements of a group with outliner setup to “Group” (popup menu)
but it’s impossible to have sub-group!
Just a sub-child is possible in hierarchical outliner.