While masking a local adjustment you can protect certain areas. But generally you are limited as per the tool you are using
If you are using control point, you can use the alt key and protect the area with another control point. If you are in graduated filter you cannot use the ALT key but you can use the Eraser in order to protect an area.
I would like to have the option that in every masking tool you can protect an area with any other masking tool.
I.e. in graduated filter, you can protect an area either with control points, or brush or smart brush or eraser.