assuming that UAT groups are mostly applied to all apps in the same manner it would make sense to enable some kind of global assignments. (like it was possible in publisher)
For now its quite painfull to assign all UAT groups ( 4 in our case ) to all apps manually. ( And update versions doubles the efforts ) .
Furthermore making changes in the UAT Ring behaviours , like changing the time between UAT groups forces you to edit alle the apps manually one by one