Apply existing path selection to layer

Do you mean a Vector Mask (Layer > Vector Mask > Current Path)? 

@christiang94431733 - As @c.pfaffenbichler notes, as you have tagged your topic with the Actions & Scripting label we need specifics to provide more than just general advice.

Press the button you have highlighted

or use Menu Layer > Layer Mask, Reveal Selection

You can of course go to Edit Keyboard Shortcuts and add a specific shortcut to that menu item. Or in Windows use the key sequence Alt L M V

Dave

It is possible. 

But what do you actually mean? Do you want to perform this via an Action, a Script, …? 

Once you have a selection and activated the mask layer you can fill it with white or black (or any grey value) to create the masked areas.