Why don’t you add a GUI color panel similar to this, that can be used to change intensity of red, green, blue (for all brightness, contrast and gamma), besides hue and saturation? It even allows you to create multiple color profiles:
This sounds like a cool effect - and the Plasma Desktop Effects framework lets you do it standalone without requiring anyone from the KDE project to work on that, and then you can publish it on store.kde.org where other people can enjoy it.
I’m sure if you code it - people will appreciate that capability.
I can’t do that. I read online some people giving up using Linux because they can’t use a color panel like the one I posted above.
you can’t win them all.
lol sure 
Eye strain should have a high priority
Night Light does work great for most people.
If the feature that you want isn’t there - it is probably because the unpaid volunteer developers that build KDE have not found it interesting enough to stop doing the other things that they believe are critical for Plasma. If you believe this feature is important - you are welcome to try to implement it yourself or pay someone else to do it for you.
I want a way to adjust Gamma in Wayland. It has been a couple years of Watland being out right? My OSD on my monitor is not a good 1, I can’t see it at all.
You can try to load a custom ICC profile in the Display Configuration settings. There’s a GitHub repo here - GitHub - ien646/gamma-icc: Gamma correcting ICC profiles - that has a bunch of preconfigured sRGB profiles with different gamma values, and also has a script that you can use to generate a profile with arbitrary gamma values.