The player cannot place a UAV or UGV into a group, in a manner similar to how mechanized/motorized groups behave.
I am aware that this is because an Autonomous vehicle behaves explicitly on the operator's command. This is a problem, as it prevents the player from scripting activities like a UGV patrolling with a fire team, as if it were a member. Instead one has to place a second group of waypoints solely for the UAV/UGV, and sync each waypoint together.
EDIT: In the mission editor, pre-made groups now exist concerning autonomous vehicles. However, one cannot manually "F2" and drag a unit to explicitly state a certain group relationship between characters.