Percussion support is basically not ready yet, but our plan in this area is that you would be able to assign unpitched percussion instruments to players, and then choose whether or not to show them as single lines or as a grid, mapping each unpitched instrument onto a five-line staff in the positions of your choosing, which would give you the flexibility to both show the staves how you want them to appear in the score and also potentially show them in a different form (perhaps as separate lines) in the parts. We will start to improve the percussion support in Dorico quite soon, though probably not in the very first update, which I expect will be focused more on improving the general snappiness of the application.