In looking at your demo site, it appears that manually registering an individual from the backend includes a dropdown field to choose the user ID. (I guess this question also refers to anything in the program that would use this type of dropdown user ID). We will have 8500 users, and I don't understand how this is possible in a dropdown menu. Can you please clarify?
Yes, the backend manual registration or editing of a record includes a dropdown for selecting a site user to be associated with the record. Having a large number of users, the dropdown will still populate. We have more users than that on this site and it populates just fine. There is a small delay of a few seconds, but it loads just fine. Thanks.