How to adjust the gray gradient in ps2020

You can adjust it with the gradient tool.

Select the gradient tool, and select "Medium Gray Density" in the lower right corner of the edit gradient drop-down option to adjust.

Medium density filter is commonly used in photography. Medium density grey mirror is used to change the proportion of light entering the lens. Medium density grey mirror darkens some pictures, usually one side is transparent, and then gradually transitions to dark gray.