Well that is all fair and good, but for me it is not obvious how to use the PhotoKit API to share a photo in a shared library. I see the isFavorite property, but no isShared property or so. Could you give me more insight how this could work?

I am not sure if we are talking about the same thing. For example the .shared func of the PHPhotoLibrary class is for my understanding a way to get a reference to a singleton representing the photo library. I am referring to the iCloud shared photo library, as described here: How to use iCloud Shared Photo Library I would like to add photos to the iCloud shared library programmatically, with AppleScript or with a small command line tool. I want to use this in my export action of another program.