If you are referring to how Bungie’s system will set your name as the one on the first account logged in with, once Season 15 goes live: -You would need to login to the game on an Xbox console, or change your name on Steam, to match how you wish your Bungie name to be set. Keep in mind that Steam display names can be changed at will. So you could change it temporarily for when the update goes live, to lock-in your desired Bungie name, and then change the Steam name back to another name. Deactivating cross-save would not help in this situation, and would simply cause more issues.