Hmmm, if you've got a consistent pattern, you might be able to use a custom property to check for each of the three properties and return the appropriate one? Eg if you've got a list of email addresses, and some users might have that email address as $email or $user_id or $distinct_id due to implementation issues in the past, you can do a custom property that just does an IFS and checks for each property if it is defined and if it is an email (contains '@' should be sufficient).
Otherwise, if you have your list in a CSV or similar, you can paste it into a filter box in Mixpanel as a comma-separated list eg A, B, C, D and that will filter to show each of A/B/C/D and you can then hit Select All etc. I vaguely remember having issues doing this with > 3,000 values though in the past.
