New Item: Part Visibility Toggler
Related Post: https://musescore.org/en/node/313572
In case you want to Hide empty staves within system, always for one of your scores, yet you want some of your score's pages/systems to keep SOME, not all, of your parts' empty staves still visible.
Then, for this case, there could be a new item (Called Part Visibility Toggler?) that you can place on 1 part (so 1 item for every part on a system you want the Hiding option in Style to not take effect on) on a specific system, in a specific page. And just like a page breaker, it will affect the properties of only the specific part ON A specific system. So what will it do?
Its effect will be visible only when applying the Hide empty staves within system setting in Style. It will basically "tell" the line it was applied on (by line I mean the group of parts which consist a line of the part in a system) that it should ignore the Hiding option, when it is enabled of course, and like that EVEN if that part's line is EMPTY, it will still stay visible.
Oh, and it will be unprintable of course.
I believe this "workaround" is really fast (at least 10 times faster than mike's workaround and keep the score cleaner than mike) , convenient and makes Musescore (V4) be more professional, as it will allow more customizability. ;)