I'm afraid the search for member feature won't help to identify members from the staff positions, not unless you know their usernames already. Knowing their usernames means, you already know their positions as well.
You can search up the positions you are looking up, "staff" or "Global Moderator" and you will get a list of all users in that position on the forum. You should also disable the 'search by name' option. There are some members with similar names to some staff positions that will show up as well.
- Jay -