Is there a way to keep displays displaying after display power off?

I want my gpu to keep displaying the screen after display power off in Windows 10, I have 2 displays and the one that isn’t the main one keeps disappearing when the display is powered off. I know this is normal behavior but i want it my way.

Os: Windows 10
Gpu: gtx 1080
Cpu: i7 8700k

I’m sorry but I don’t think your question is clear enough. You want the system to keep detecting a screen connected to your PC even if it’s powered off?

Exactly

I don’t think it’s possible since you’re basically disconnecting it from the system. The only thing you could do (which I don’t suggest you to do) is opening up the monitor and hook up a switch that turns off the screen itself without turning off the monitor controller.

You could try to put an EDID-Emulator in line with the primary monitor and the GPU.
Then the GPU would always “see the display” even if it is not connected/powered off.

Those things are a bit on the pricey side though.
Example

Look at an e-paper / e-ink display.

What is the end game? I don’t quite understand but …

Do you want to have the monitor signal detected by the GPU in your system all the time even when the monitor is physically turned off / unplugged? In that case, I would use HDMI Headless adapter. Yes, it requires physical interference in the cables / port but it can be automated with the help of hdmi switch. And just switch the source from the monitor to HHA and gpu / os should still think that the monitor is connected / turned on.
https://www.newertech.com/products/hdmi_headless_video_adapter.php

Or maybe you want the other way? For monitor to detect signal when gpu is off / disconnected? Then something like EDID 101H 4K.
https://www.extron.com/product/edid101h4k

Pretty shure this is what I want but a display port variant if they exist.