A new library begins with a single group set titled My Groups. However, you can create up to 5,000 group sets in your EndNote library.
To create a group set:
From the Groups menu, select Create Group Set.
Enter a name for the new group set.
When you first create a group set, there are no groups listed below the heading. You can drag groups to move them from other group sets to the new group set or you can create new custom groups, smart groups, and combination groups under the new heading.
Selecting a group set shows all the references from the various custom groups, smart groups, and combination groups under the set.