Sub groups on DUG are special interest groups, niche groups or regional/local user group chapters.
All members can start a new group, if you have a group of a minimum 5 members who likes to join. If you like to start a new sub user group here on DUG, then contact the site or parent group owners (via the contact link on the group front pages).
Where it's free and open for all to join our parent groups, then sub groups may set membership requirements, like who is allowed to join and under what conditions. Request information from the group owners on how to apply.