I agree with k_b on this issue – if I want to hide a cautionary clef, key or time signature I shouldn’t have to break the music into different flows. That interrupts the “flow” of my creativity when I’m trying to produce an elegantly printed musical work. I hope that someday we’ll be able to hide or show, in score or in any/all parts, whatever we would like to see or hide. That is one of the most helpful aspects about Sibelius – it makes it so easy to get just what I want on the printed page.