I run three screens for my flight sim 27", one 24" for my EFB and one 7" for my Attitude Indications panel.  Never had a problem before as the 7" screen was the last one added recently.  I have the correct drivers for all screens.  Every so often the screens change, my flight sim goes to one 27" monitor and my attitude indications goes to my 24" monitor.  I have googled windows 10 info and cannot see anything to help me.  I use Simple Runtime Windows Editor to set the screen resolution across the three sim monitors.  Thanks in advance.  Laurie

I don't know the Simple Runtime Windows Editor, but you basically how to possibilities with P3D: either run Eyefinity or Surround, or simply stretch P3D over 3 screens and hit alt+enter. Don't need any 3rd party tools for that.