Indeed, passing a .rootContainer as fileIdentifier does return a URL like: let url = try! await NSFileProviderManager(for: myDomain)?.getUserVisibleURL(for: .rootContainer) but then: NSWorkspace.shared.open(url!) shows an error dialog: The application “MyApp” does not have permission to open “MyApp-FileProviderExtension-1.”

Completely another approach would be to base the implementation on macFUSE but that would require installing macFuse kext extension so I'm not sure if it is suitable for you...

Interesting note on childItemCount for updating file's parent when file is created in folder. In my current FileProvider implementation, I don't track the childItemCount property so I don't update the parent. What are the benefits of tracking it? Am I in trouble if I continue to not report the childItemCount property? (I know we're moving away from the main subject...)