I've been running the betas fine for a while, now, where do you want to go??

hi. I have a MacPro 2019, and I'm running Monterey at the moment. I have three screens. Two 4k screens, and a XDR in the center of them. My MacPro 2019 boots with the left screen showing the startup and login screen. I've previously had it boot to my XDR before the others. I'm not entirely sure why it moved to the left, but I need it back on the center screen. We used to just drag a happy mac icon from screens in the displays system preference. I don't see any method to change this startup and login screen. How do I choose the permanent bootup and startup screen (as my XDR!). Thanks. Dave