Hiding staves

Yes, but it depends on what is in the choir part. You only have to unhide hidden staves of course.

When you use "Hide empty stave" make sure you remove the check from "Don't hide empty staves in first system" (or whatever that says). Now, as long as there is something in the choir staff it will be shown. If not, the easiest way to unhide a hidden staff is select the last note or rest in the last visible staff and press the right arrow. Enter a staff text (I usually use a single . for this) and the staff will become visible. In the inspector, turn this staff text white so it doesn't create a blemish in your score. Select it and copy it. Now after this, when you want a staff unhidden, use the select last visible note/rest, right arrow and paste it using ctrl+v as needed. I actually have a white dot in my palette I use for this purpose. It's in a custom palette between two things that are not white so I know where it is. This way I don't have to make sure it's on the clipboard.