there are ways to customize the toner ink curve alone. But there is a lot of trial and error, when another another paper or other display light you may want it changed on a given image. My conclusion was to put more than enough color ink in any given curve (other than the K only curve) than I would generally want, then use the sliders to tweak through the scale on a given image.
It's a brilliant system, but one thing it doesn't do is help you find dead neutral as a starting point. But we never had that in the darkroom either with our bromides and chlorobromides and paper developers and additives and toners.. it was all visual and talent. Caponigro.. for example...
There are more sophisticated QTR users than I, so looking for other input would be helpful. I play with QTR when I need to, but primarily use Ergosoft for that work.