pv currently allows the user to create multiple equivalent channel groups by just running the "group" action multiple times:
1.) Select the first two channels.
2.) Run the "group" action from the context menu.
A new group for D0 and D1 is created.
3.) Run the "group" action from the context menu.
Another (equivalent) group is created.
I don't think there's a point in created equivalent groups, so the GUI probably shouldn't allow it.