I’ve set up a project with two alto sax and two trombone players. In Setup I’ve added a new instrumental layout with both trombone players. Flow 1 will include both players, flow 2 will only show the first player (the second has rest). Now flow 2 show also the second player. Is it possible to hide them?
Can’t you just exclude the second player from the second flow? (In Setup Mode select the second flow in the bottom panel and deactivate the player in the left-hand panel.)
Hmmm… Yes I have tried it first. I don’t know what was going wrong. I have follow the steps and that works.
I thought there is also an option to remove empty parts from a score.
Yes, you can remove empty parts from the score through Layout options (cmd+shift+L) → Vertical spacing → Hide empty staves. But depending on what you want to appear in the part, Florian’s solution might be better.
Thank you! I was looking in the Players and Staves/Systems for this option. It was in the vertical spacing 
This is exact the option I searched for.