How do I mask an new object created? (system create object)

system create object and pin to bg..

and

masking layer Behaviors > destination out

but

masking does not work..

It's not clear from your screenshot how your layers are organized. Mask will only work for objects on the same layer and you need to set "Force own texture=yes" in layer properties.

Force own texture yes selected..

Everything that is not created with create object is masked but only those created with create object are not masked.

All objects in layer same..

(sorry, I do not know English very well. :))

could be that the new object is above the mask object. Try sending the new object to the bottom, or move the mask to the top after new objects are created.