How do you manage other groups that are not patrols or dens

We have several groups in our unit besides the scout patrols. Examples are (OA scouts, PLC, High Adventure trips, Troop committee, Eagle COH planning, etc.) Our previous website allowed us to create these the way that TT creates custom mailing lists. Once that group was created they could be invited to events.

Without this functionality we are currently using additional patrols but it makes a mess with several youth in multiple patrols. Am I missing something? Is there a way to better manage this that I am missing? From some old responses it seems like this may have bene a functionality that was removed?(!!!) Looking for some help if anyone has any suggestions.