If you go to a member's profile page in Leader and Clerk Resources (LCR.ChurchofJesusChrist.org), there's a pencil icon on the right that you can use to edit the member's information. There are a few different name fields. The "Current Legal Name" field should have their full name as it would appear in legal documentation, including middle name(s). "Preferred Name" is the "public" display name that shows in the ward directory and a few other places.
Samuel Bradshaw • If you desire to serve God, you are called to the work.