Group memberships
Users can be members of any number of groups. If a user is not a member of a specific group and not an administrator, he cannot log on the onion.net editor.
User administrators add a group to user memberships by dragging & dropping, i. e. the group is dragged from the group administration directly into the grey area and thus referenced. A group can be deleted via the context menu (click on the group name with the right mouse button).