You said, "Looks like sub-groups won't be useful - as I had hoped - for temporary, private, attendee communication and resources for one-time events."
I use a lot of sub-groups, and some of them are for "temporary, private, attendee communication and resources for one-time events." What I do is re-use the group for the next event, and use the wiki to list ALL the events, and links to the summary message if there is one, or just the name & date.?
For instance, I have a public Conferences group, which has been used for quite a few different?meetings that some of our genealogy society might attend, and tell other interested folks about the sessions they attended, sales on products available during the conf., etc. You can see the group at?. When a new conference opens for registration, I just change the display name, update URLs etc. I made it because there were complaints in the main group about these conference discussions.
I've done the same sort of thing with various study groups we've held, keeping track of them in the Wiki. Changing names and images is easy-peasy, and it's much easier to reuse a group than to delete and make new ones all the time. I don't echo the discussions in the main group because the point of a subgroup is that those who want to discuss there, will. Those who don't can ignore it. If they change their minds, and the group is public, they can always go back and read the discussions later.
I would caution against copying private messages to make them public. Doing this might cause hard feelings. If you want to delete the private group, change its name to some nonsense first so you aren't locked out of a name for your future group.?
Best,
Valorie
-- she/her. "Dwell on the beauty of life. Watch the stars, and see yourself running with them." -?Marcus Aurelius
Valorie Zimmerman