Cadence Virtuoso - Cell Parameterized
I am guessing that under Options->Display there would be a way to choose number of layers. You can explore LSW a bit more. 


There is a difference between selecting and displaying layers. If you are not sure, you can end up moving entire chunks of layout leaving contacts/or something else behind.
The error message on screen is obvious (You can't edit the layout of a pcell). You can always define your own cell and edit the copy.