In Bug 30515, we are discussing adding a new system preference UsePatronPreferencesForOverdueNotices to let patrons control which overdue messages are sent by mail in their messaging preferences. For many libraries it would still be necessary to set a certain overdue notice (say the third overdue notice) as "mandatory for print message". Jonathan suggested to reuse the aforementioned pref and make it multivaluated with 3 values possible: ODUE, ODUE2, ODUE3. Then: - if at least one is selected then patrons can edit it/them - if none selected, we don't allow the patrons to modify any This would be the simplest way to extend the functionality of Bug 30515.