To define a new view, you must visit the menu "Configure special groups" at the end of the policies section of the user account menu. You are presented with a list (originally empty) of configured groups. Use the Add button to add a new configuration.
Pick the group you want to manage and assign a login shell. You may want to pick either /bin/false for unprivileged accounts and /bin/sh for normal accounts.
Once you have define a special group, a new privilege is added and you can grant this privilege to any normal user. He is then allowed to manage this group members.