This thread talks about instant print preview.
What is that? I can’t find it in the manual (3.5.12).
Are they just talking about the Print tab?
It’s the fact that pressing @ key, every UI signs (signposts, coloured voices, etc.) disappear and you see the music how it’s going to be printed, on your screen. I think it was introduced in 3.5.10, so you should find it in the version history.
Edit: sorry, both answers before mine did not show up in my mail box, and of course my @ key is the French key, which is not the “official” one (and probably not the OP’s keyboard layout).
BTW, the manual isn’t quite correct here as “you can also hide/show individual non-printing elements permanently” isn’t true with Chord Symbol Regions. I suspect this is an error in implementation rather than an error in documentation, but in any case there’s no way to hide the purple bar at the top of a chord symbol region other than using print preview. Turning off Highlight Chord Symbol Regions removes the highlighting of the measures, but not the purple bar on top unfortunately so there’s no other way for users to hide it.
That’s true, but I’m not sure that one specific instance needs to be clarified in what is essentially an “fyi” pointer to the linked topics below 
… and hopefully will be correct in the next version 
Hey @Lillie_Harris,
I can’t find this function in the key command settings. As I use a German keyboard, I did change the key command a couple of years ago. The key command doesn’t work for a quite a while now. Today I wanted to change it but I can’t figure out how this function is called. Obviously it is not called “Hiding non-printing elements” like in the manual.
Thanks in advance.
Jan
I believe in German you will find it in the Key Commands page of Preferences by searching for Nicht druckbare Elemente ausblenden.
You can switch between the English manual and translations by swapping out the language code in the URL. So where the English page has /en/, replace that with /de/ for German. In this instance, the exact name of the key command isn’t outlined aka “You can change the key command for X function…” but helpfully, the title of the topic in German matches the string, which could give you a pointer in the right direction!
(The only time this doesn’t work perfectly is if the English manual contains topics that haven’t yet been translated, and therefore those pages don’t exist in the other languages.)
Thanks @Lillie_Harris & @dspreadbury for your quick replies.
By your hint to the German manual page, I discovered that I already use the key command for the German keyboard, which is Shift-° (macOS). But it doesn’t work anymore.
I wanted to see if I could change the key command.
But I guess, I wasn’t clear enough about the actual problem nor the settings I use.
I use a German keyboard (Setting to German keyboard), but the Language of Dorico is set to English. So the function which I’m looking for is “Hiding non-printing elements”, but this doesn’t seem to be the name of the function in the key commands. So I just couldn’t find it.
So my question is: What is the name of the function in the key commands page of Preferences in English?
Aha – in English, I think it’s “Hide Invisibles”.
That’s it! Thank you so much.
Strangely, no key command was stored under “hide invisibles”. But now it works again!