Digital Light & Color

I think that it would be a useful improvement if the Three Zone Adjustment combined masks on the Blend tab partly overlayed the input image as do the individual red masks on the Highlight, Shadow and Midtone tabs.
It would be helpfull particulary with higher transition blur radii when the borders between zones merge a great deal and it is not always clear which of them prevails where.

I guess that Two Zone Adjustment could profit from it as well.