Ability to Split Two Hand Piano Score

There is no easy way to only play the left or the right hand because muting effects both the L and R hand. All of the help for doing this w Muse4 fails to work, for me.
People often want to practice playing either the L or R hand, or to use another instrument to play the L or R hand.
It would be really great to have a menu item that would let you with one click separate the L and R hand.

Thanks