Windows displaying monitor when not active

[Trojan Horse]

I have dual monitors.

I plug my PC DP into my main monitor (LG 34UC98) and the second display.
I plug my work HDMI MacBook into my main monitor only.

I want Windows to recognise that there is no monitor when my input is switched to HDMI and I cannot see a screen.

This is annoying because I have my HiFi setup on my PC, so If I want to listen to music I have to keep switching inputs, even though the input is not active, Windows apps are moved to that window I cannot see.

It's a small thing, but it's been annoying me for many years now so I figure at least one person might know how to fix it?

 

[Biz.Kid09]

If you do; Win button + P you will see various options, you can show on Display 1 or 2 only or extend and so on. Have you tried playing with them options to see if that works for you?