copy / paste single layer

Hi all

I know there is a way to do this, but I don't know the right keyword to search the forums by:

I am trying to copy a single voice, and paste it onto layer 4 of a staff that already has music on voice 1.

I have already changed layers of the item i am copying, but pasting erases the stuff on voice 1.

is there a "paste special" type of function?

Also, is there a way to delete a single voice only?

thanks

musescore 2.0.0
mac OS 10.7.5