[brazen1]

To be clear, so there's no margin for error on my part, you wrote "My XDR app can work in any GUI interface outside kodi. You would simply click on HDR on.exe anywhere on your PC to activate."

Unless I'm mistaken, simply downloading your 2 .exe's and clicking on them anywhere should enable and disable HDR globally. Is this correct?
I have setup MPC-HC and MPC-BE, per your video and pasted the exe's within their default install folders also fwiw. Tried many, many things but the outcome is always "External Player Active. Click OK when playback has ended".

I believe it works for you, but not for me. You asked for testers and I'm giving feedback. You are using AMD GPU. I'm using Nvidia. You say it doesn't matter and I believe you. It's hanging at step one (enable Windows HDR). I presume that is the only thing HDR on.exe does but nothing is happening, not even a CMD flash.

I notice in your video you are using ffdshow but disabling it. I don't have ffdshow installed because I don't need it for anything else I use. Does that matter?

Other than what I've reported, I don't know what else to give feedback about unless you ask.