Hmmm, I can’t think of a good answer for the key signature issue, other than making the first one purely graphical and then hiding accidentals as needed on a note by note basis. That would be quite a lot of effort though for something that is just 1 click in Document Options in Finale. Maybe someone else will have a suggestion.
Hiding various elements has been a much requested feature. For now to hide the cautionary clef you either need to start a new flow in the next system, or just add a Coda and hide the Coda symbol. As the latter is much faster, that’s usually what I end up doing. Here’s an example with the signposts showing:
I fully agree that there should be easier ways to hide elements without these sort of workarounds.