We would like to be able to import people and their RSVPs to events. I thought that if I gave them all a tag, and then searched for that tag that maybe I'd be able to mark all of them as RSVP'd for xyz event - but that doesn't seem to be possible. Is there a way to do this other than marking people one-by-one as attendees?
Alex, currently the way to add offline RSVP's to an event is by adding them individually under the Event settings. You would go to Event Details>RSVPs>New RSVP. See below a sample of the page:
Also, if you have a large list of offline RSVPs and don't want to enter them individually, you can still add them to the count. If you go to Event Details>Settings and fill in that number under "Additional # of RSVPs to add to the total" you will be able to update your count.
If you want to keep track of offline people that have attended your event, you can always import the list and add the same tags to them that the event page adds to RSVPs.
Complete and current information on how to use NationBuilder is available in the documentation section.