@stefan.chirila - thanks! for the screenshots.
Channel Mixer isn’t the same as using the RGB multipliers to set a white balance. I’m assuming that Channel Mixer operations are done after the image is already white balanced, and also after converting the image from the camera input profile to one of the RawTherapee working spaces.
The Raw Black Points sliders are somewhat the “black point” equivalent of RGB(G) “white balance” multipliers, and if RawTherapee already had RGB(G) white balance multipliers, then the white balance multipliers could be set to 1/1/1/(1) and then the white balance could be set using the Raw Black Points slider, at least in theory.
Sometimes I do use the Raw Black Points sliders in RawTherapee to pull the “noise floor” down a bit. But to avoid adding a color cast to the image, it’s necessary to move the Raw Black Points sliders proportionately to the white balance multipliers, which RawTherapee doesn’t supply.
Right now when I want to move RT’s Raw Black Points sliders, I use a spreadsheet, inputting white balance multipliers obtained from UFRAW, which produces colors that look more or less right. But I’d feel more comfortable if I knew for sure what white balance multipliers RT is using, if indeed RT really does use white balance multipliers to set the white balance.
Though this brings up another question: How is the white balance in RT actually calculated? I have a feeling it’s more complicated than just adjusting the RGB(G) multipliers.