In “Full Score” layout, I usually don’t really want to see chord symbols more than once. I usually set the piano instrument (if I have it) to show chords in full and part layouts and all other instruments that need them to show in parts only.
However - this approach doesn’t work well if I have a part of the score where the piano is not playing, and I’d rather its staff being hidden (I have "hide empty staves). Because I elected the piano to always show symbols - I get it showing as a redundant empty staff.
How do I accomplish:
Chord Symbols in full layouts appear once but they always appear.
I can hide any empty instrument, without assuming that an instrument (piano) will always have content.
If this is not what you want, you can also set each player to Hide chord symbols. But be aware that if you later create a chord symbol on that staff, it will show all chord symbols (until you reset that option in Setup).
Chord symbols are not used much in my workflow. So I’m afraid my response is: (a) I don’t know (though perhaps chord regions might help you?) and (b) why would you want to, when showing them above the top staff does not care what instrument is at the top (I mean - for whose benefit are you showing the symbols?)
Because if there is a rhythm section instrument in the score, it’s easier to read the chords next to it, but if there isn’t I would still want to see the chords.