My monitors:
[A] and [B]
On the monitor B I play all my games, be it CSGO, LoL, PubG etc. Everything is recognized on the monitor B. I also set this to the main screen. Still, when I start Minecraft and launch the game, it stays on monitor B. BUT when I go into fullscreen (F11), it switches to my second screen over without a reason, and without a full screen I can play the game very hard because otherwise it jerks too much. I COULD maximize it (double-click on the titlebar) but unfortunately I have no fun doing it.
I hope you can help me, I own Windows 10 as operating system.
Try to take the game with the mouse on the taskbar and pull over to the other screen. Shut down. In the best case it is changed.
Unfortunately that does not help, because if the game is open it will appear on both screens on the Taskbar.
I'm afraid, then nothing will help. Then the presentation will be coded on the screen in the program of the game itself. If there's a time that says about "maximize image at edges of… Anchor to…" then you can do nothing from the side of the operating system. I do not know if that is the case, but it can be good.