A piano music is usually ,written on two staves. When I listen to it, it plays the both voices together. How is it possible to listen to only the right (or the left) hand ?
In the play menu, you can select the voice you want to hear
For the time being this is a little awkward to achieve, because playback is muted or soloed on the basis of whole instruments, not individual staves within an instrument. You can use independent voice routing in Play mode so that each voice goes to a separate channel in the VST instrument. Then you can mute specific channels in Dorico’s Mixer to hear a subset of the voices on the piano instrument.