You can’t do this in Dorico Elements, I’m afraid.
I can’t seem to get this to work. Am I supposed to edit the key commands file found in the user folder in App Data–Roaming–Steinberg–Dorico 2?
At least on mac it’s part of the Dorico package, in Contents: Resources.
No, don’t edit that one! Edit the one in your user Library!
/Users//Library/Application Support/Steinberg/Dorico 2/
What is the difference? That’s the one I’ve edited, with no problem. Genuinely asking…
The file that is part of the Dorico package is the system default. If you edit that, “restore to defaults” isn’t going to do what you expected. It will also get overwritten if you re-install or update Dorico.
The “user” file won’t get overwritten, and if there are multiple accounts on your PC each account has its own user file, which might of course have different edits.
I don’t know how file permissions work on Mac, but on Windows, if you are running from an account which doesn’t have Administrator access (which is a good idea from a security point of view) you don’t have permission to edit the “system” file, but you can edit your own “user” file.
(Having said that, many people on Windows only have one account set up, and in that case Windows does give the sole account administrator permissions automatically - otherwise it would be impossible to do any system admin tasks, like creating a second account!)
It will probably disappear with next update. The one in your library remains 
First and foremost: that’s not the file that gets altered when you make changes in the Preferences interface. So you now have to manage two files instead of one, and ensure there aren’t any conflicts.
As has been said, that file is part of the application itself, so will be over-written in the event of an update, or if you need to re-install.
Dorico 3 might import the user settings from the v2 user folder, but it won’t look in the v2 app.
The alterations made are ‘hard-wired’ for all users, not per user. Non-admin users can’t write to that location, either.
If you only modify the user files, then you can restore the app’s defaults by deleting the user file. When troubleshooting, you’ll know that the app file is a clean copy and not at fault. You can re-install Dorico and keep your prefs intact.
It’s easier to manage backups if the file system is divided into “Read-only” areas like Apps and the OS, and more variable content within the user domain: e.g. You can restore your entire User Library preferences folder, without having to go into each app and separately restore components.
These may not be an issue for you, but it’s in line with good practice in file management and data security. As you may have noticed, Apple is making it harder for users to manipulate files outside their user domain, and this is set to continue into Catalina.
Because it gets overwritten every time there’s an update. There’s no need to make changes to the one in the application.
Yes, I did have to rejig the file when I updated. Thanks for the info. I’ll do the other one.
One alternative—if you have a stream deck—is to program a multi action. I’ve done this and like it. I tell it to switch to engrave, hit shift s and then switch back to write mode. It’s a bit of a hack (in the sense that it is outside of Dorico) but it works.
…unless Engrave Mode was previously set to staff spacing, or frames, or note spacing. 
The system and frame break shortcuts work well in Write mode, as long as you don’t have a complicated multi-frame layout. Those stream deck multi-actions are great for different kinds of tuplets!
True. Sigh. One of my biggest frustrations with the current build is when I make an extensive multi-measure selection, switch to engrave mode and lose everything, all because the last time I visited engrave mode I tweaked some note spacing and forgot to turn it off. 
Romanos, do you know you can assign a key command to any of those 4 functions in Engrave Mode? They’re under the Edit category.
Edit Frames
Edit Graphically
Edit Note Spacing
Edit Staff Spacing
I just discovered this, and I’ve assigned an extra step in my Stream Deck macro to ensure that Engrave Mode switched to the Graphic function before adding a frame or system break. Voila.
Dan, many thanks. I must admit, I got my stream deck (and my Alesis keyboard) and set up my most used functions, and haven’t perused all the other available key commands as throughly as I should have.
Maybe this is common knowledge for most of you already, but I just realized that you can create a system break in Write mode simply by Alt clicking after selecting the signpost for an existing system break. I didn’t see this way of creating system breaks mentioned in the documentation.
It seems sort of odd that you have to create the first System break in Engrave, but then can only Alt copy it in Write, as Alt clicking with a break selected does not work in Engrave. Anyway, maybe I’m late to discovering this feature, but at least it’s another quick way to assign System breaks without leaving Write mode as long as you’ve created at least one in Engrave first.
Nice trick, I’ll use it! Thanks for sharing!
It’s perfectly logical, which might explain why it seems weird compared with other software
Alt-click just copies things. That will certainly be explained somewhere in the documentation but there is nothing special about copying a system breaks compared with anything else (notes, dynamics, text, etc…)
And you can’t copy things in Engrave mode, because that’s part of the difference between Engrave mode and Write mode.
IMO the real “logical anomaly” is that a system break is actually a thing, so you can copy it. But if it was just a property of something else, e.g. a bar line, you would only be able to have system breaks at bar lines, which wouldn’t be much use if you use open meter with no bar lines.
Just remember that if you Alt+Click a break to copy it, any properties attached to that specific break (staff labels, Space size etc.) will also be copied.