@Mark and @david BTW I originally was going to use the unique ID feature to make the link relationship on the Attendees spreadsheet but realized that it wouldn’t work for this many to many style of relationship because of the choice component. When adding an attendee to an event either from the participate detail side or the event details side of it, both need to use a choice component to select the other side of the relationship, and since the choice component only allows you to select on column, using the Unique ID column would be useless.
See my post about an enhancement to the choice component: