We have an experimental option on this, though it's not well tested. Edit the GameUserSettings.ini file in your local data (C:\Users\<user>\AppData\Local\HeliumRain\Saved\Config\WindowsNoEditor on Windows, ~/.config/Epic/HeliumRain/Saved/Config/LinuxNoEditor/ on Linux).

Look for (or add) "MonitorNumber" in the section "[/script/heliumrain.flaregameusersettings]". Here how that works :

• 0 means "default"
  
• 1 is the first monitor from the left
  
• 2 is the second monitor towards the right

Thanks for at least giving us some way to configure this, just bought the game after watching some videos and almost thought I'd have to refund because I couldn't bear to crane my neck left on the 3 monitor setup.