Typical, I ask a question then hunt around some more and find it in the dashboard, I’d assumed there would be some way from the group pages on the main site.
You can add members to any group, hidden or otherwise, by going to Groups > Edit Group in wp-admin.
I find this plugin incredibly helpful when managing — and allowing others to manage — the membership of groups, without availing them to the dashboard: https://wordpress.org/plugins/invite-anyone/
Thanks for the replies, I’ll check out that plugin as well, looks like it could come in handy in the future.
mrjarbenne, can you answer a question about how the plugin is supposed to work? I installed it a few days ago and am working with site testers. I invited about 20 people initially. A couple of days later there are new members and I want to invite them. 2 things:
There are still some people in the right side column who never accepted the invitation. If I add more people to that list do they get the invitation again?
Also there are people who are already in the group (they accepted the invitation) who are back in the directory on the left. But not all of the people in the group are still in the directory.