Masking in Grease Pencil (2D-animation)

This is a very important tool in 2D animation. With his help eyes, movements of the mouth and much much more are made. And this has nothing to do with composing … Especially since the tool already exists and it works, there is simply no grouping on the layers and it is not possible to assign to which layers the mask works, and where its action stops. Here are some examples: blenderartists.org/t/masking-in-grease-pencil/1141149