And generally, use components instead of groups.
As DaveR has said himself, groups are only a special form of component, with one small advantage, and two bigger drawbacks.
The small advantage (for some) is that they don’t appear in the Component Browser.
The drawbacks are that editing a copy of a group doesn’t change any other copies, whereas editing one copy (‘instance’) of a component changes all the copies.
And if you delete a group from the model, it’s gone. If you delete a component, a copy of its definition is retained in the Component Browser until you deliberately ‘purge unused’ or delete the definition.
If you want a slightly different copy or copies of a component as well as keeping the original, R-click on one or more of the copies, and Make Unique. Any edit to one of the selected copies will change all the others to match, but leave the originals unchanged.