Geometry switching is what you want, if it's a body part in a figure (CR2). Alternatively, a visibility pose will give the same effect but through the library interface. 

For making a PP2 prop disappear, geometry switching is unreliable, but you can use a morph which will shrink the prop to zero and/or whizz it offstage smartly.

I'll get back to this thread later - have to work now. ;-)