So is it possible to add one more automatic checkbox to Channel mixer to automatically balance only 2 sliders and always keep third slider at 100%? This could be useful for crosstalk correction purposes and other special effects.
Also here is an UI idea. Why don't group channel mixer sliders in single tab instead of 3 tabs and also add names to them like this? This will allow mush faster operation because no need to switch between tabs. It is also nice to see all values together. And also due channels naming is much easier to understand Channel Mixer logic.
Red in Red
Green in Red
Blue in Red
Red in Green
Green in Green
Blue in Green
Red in Blue
Green in Blue
Blue in Blue
As very nice example you can see this channel mixer plugin for Davinci Resolve https://mononodes.com/rgb-crosstalk-dctl/
Here is also video explanations how it works
https://www.youtube.com/watch?v=RkzOTKl7zrs
https://www.youtube.com/watch?v=XCvsZ8WDKyY
Also in some channel mixer tools have build-in Hue and Saturation per channel sliders which also useful during color correction.