You can create your User Mention Groups by access the “Manage User Groups”-Page from the profil dropdownlist.
On the Configuration Page you can manage your existing groups “Manage Group”-Tab or create new Groups “Create Groups”-Tab.
To create a new group, select the “Create Group”-Tab:
Enter a name of the Group and add member to the group. Just start typing the name and select an user from the list.
After a group is created you can access the group inside the “Richtext Editor”. For example during a issue creating.