I have eight separate photo libraries with tags that overlap, so I don't want to combine them (it would be a mild nightmare). I'd like to be able to switch the system photo library without opening Photos/choosing a new library/changing the system library in preferences. Is this possible? I cannot find a subroutine here that seems to accomplish this, and I can see some of the constants that change (in various plists) when I swap libraries, but apparently I haven't found all of them, as my attempts at a swap have failed.
How do I switch the system photo library without opening Photos?
The only way to switch the system photo library is via the Photos preferences window. I recommend that you file an enhancement request using Feedback Assistant to request the functionality you desire.
> I can see some of the constants that change (in various plists) when I swap libraries, but apparently I haven't found all of them
Does the application you're making have the same free reign to both /Library and ~/Library?
I'm looking at Photos plist prefs (aka various), not photo libraries.