The Account Owner or a Super Admin can create User Groups from the Users panel within the form builder.
Once a Group is created under the Users panel, Users can be assigned to this Group. Users can be moved to other Groups at any point.
The Group Admin (role available only for Enterprise accounts) can create new Users as well, but only within the Group they are assigned to.
If sharing is restricted at the account level (globally) by the Account Owner, then only the Super Admin or Group Admin can give access to a form or folder outside of a Group.