Allow multiple selection for the new per-system "Hide empty staves" function

Your idea

The new function to be introduced in 4.6 allows you to select exactly which empty staff has to be show in every single system, a long waited and very welcomed function for a lot of useres.
Anyway, currently (4.6 alpha and the last nightly), you can only select one system at a time.

...Oh, well, apparently you can select multiple "eyes" holding Ctrl while clicking, but the widget only shows up if you select the eyes one by one.

Problem to be solved

It is very common that multi-movements works have different orchestration for each movement: just think about any Bach's Cantata.
Selecting every single staff to show only the instruments involved in each movement could be very time consuming: instead of his Cantatas, try imaging reengraving the B minor Mass...

Having the widget to popup on multiple selection and affecting more systems at the same time would be an amazing step forward for this new hiding function.

Prior art

Just for info: I come from years of using Sibelius, where the hiding system is different: you just select a range of measures (on any instrument) and with a shortcut you have the list of which istrument you want to be show in that range (which of course will affect the measures outside that range which still are in a system where the first or last measure of the range are).
It's pretty obvious that MS works very differently about hiding instruments, it's just for general info.

Additional context

No response

Checklist

• This request follows the guidelines for reporting issues
• I have verified that this feature request has not been logged before, by searching the issue tracker for similar requests