How to make independently editable copies of the same node group? I'm working with a node group (&#9096; CtrlG) and I would like to make an independently editable copy of it. 

When I'm making a duplicate (&#8679; ShiftD), there is a second node group created. However, whenever I make changes to the nodes inside this copy, the changes are also applied to the first group. How do I avoid that?
Click the little number next to the name of the node group after duplicating it:



This will "unlink" that node group and make it into a copy, so that editing it will not change other instances of the group it was duplicated from.

The number refers to the number of "users" of that datablock, i.e. the number of instances of that node group.