Can I ask what exactly you mean by grouping?
You can already assign your selected units to a group (1-9) by pressing, for example, `Ctrl+1`. You can then select that group again later with `1`.
There's a lot you can do with this, especially when you start combining it with the other selection controls. For instance:
- Double-click a raider to select all raiders of that type on screen
- `Shift+1` to add Group 1 to the selection (maybe it contained some riots)
- `Ctrl+1` to make that new, bigger selection the new Group 1
And then send them off to go kill some stuff.
I guess what I'm trying to say is there are already a ton of advanced controls that aren't necessarily explained. If `Ctrl+[0-9]` isn't what you need, maybe you could give a specific example of a scenario where you're having trouble?