This needs to exist. It brings me immeasurable frustration that it does not. How painful is it to go and replace every single note with a different instrument if you don’t like one that is used? Quite, I think. So there should be a button to automatically replace all instances of an instrument (options for on one layer, one sheet, or everywhere) with another one.
If someone has already suggested this, I’m sorry, I didn’t look. But yeah.