I mean, something similar to running the eyedropper/crosshair over the image and seeing the information in the Info tab or seeing where on the Curves line the pointer is. But to see it on the histogram and be able to leave a marker.
Hoping to clarify what I said in above post if I wasn't clear before.
If you want to apply a 'zone system' to your image then the tools are already there. Within the Curves dialog. It has a histogram (curves display options). Zones can then be assigned. Choosing the eyedropper, or TAT tool in the new versions, and then running it over the image will tell you which 'zone' applies to which image section. The 10 point curve grid (option click on the curve BG) will also help here.
A histogram tells you what the quantity of values there are at different grayscale levels of the image, and as such has limited value in visual terms. I've always had a theory that Ansel Adams for the time very 'scientific' tonal zone system - actually has its strength in the fact that it leaves room for interpretation.