Hi There: I think we understand each other. You're asking about develop presets, and if there's a way to proportionately reduce the effect of a preset in Lightroom. To the best of my knowledge, the answer is no. The reason for this is that Develop presets can contain not just information from the basic panel (Exposure, Recovery, etc.), but can also include vignettes, cropping information, split-tones, etc. Virtually every aspect (or only one) of the Develop panel can be used in a develop preset. So, if you want to tone back and your preset includes both sharpening and noise reduction, do you fade back the amount of sharpening, the radius, detail, and masking as well as the black point? I mentioned the brush tool only because if you make a selection with the brush and set one or more sliders, you can proportionately adjust the sliders FOR THAT BRUSH by clicking and dragging on the pin.
Mike.