I've looked around quite a bit at the EventKit documentation and done all the searching I could think of, as well as examining the EKCalendar and EKEventStore types. Trying to find out how to view, modify, and create groups of reminders lists.
EventKit Reminders Groups?
It's not currently possible to view, modify, and create groups of reminder lists through EventKit. The best way to request this functionality is to file a Feedback Assistant with this enhancement request.