It’s a bit of reading, but I think this thread (especially the linked post) is a good place to learn more and understand how to preserve midtones while adjusting highlights and shadows/blacks in PhotoLab. Note that there are other consequences to tonal adjustments in both Lr and PL, depending on the method you choose.
For more precise control of tonal ranges in PL, maybe the tone curve tool is the way to go? It may be more clumsy than a handful of sliders, but has no side effects or ambiguities.