roto shape adding child

When you have two shapes in a RotoShape node,
and you make Shape2 a child of Shape1,
it does not affect visibility. You can turn
Shape2's visibility on and off in the Parameters panel.

Of course, if Shape2 is completely inside Shape1,
and they are both white, you won't see Shape2.

If you want your child shape to be a hole in Shape1,
make Shape2 black (right-click on the shape's
transform control and select Black).