I'd love to know - have you had any luck finding it?

1st thing I'd try would be using the latest Xcode 14 RC. (Sorry I posted before reading the comment & reply below).

Seriously this is all I want from WWDC this year. Alternatively maybe the developers of Pixelmator Pro can be persuaded to open-source or license their implementation of this feature....

Thanks - I'm busy converting a project from CoreData to SwiftData, then I'm going to tackle this next -- needless to say, I was thrilled to see they've added it, and glad to hear you've got it working.