I've examined the Keyboard Shortcuts section under Application Menus in Photoshop CC 2018, but there seems to be no way to add a keyboard shortcut for Add Layer Mask. I use this feature all the time, and having to always mouse over to the icon is cumbersome. Isn't there a way to assign a shortcut to that command?
I've tried via the Action Menu but that doesn't work either. It's strange because other Layer Menu commands like Add Layer or Delete Layer are easily assignable. As you can see from this menu shot, even though Apply Layer Mask has Shift+Command+M assigned to it, that doesn't work either.
Is there something I'm missing? Or is it impossible to assign a keyboard shortcut to Add Layer Mask in Photoshop CC?