Code Data's diagram editor style facilitates powerful collaboration on an app's data model. Apple, please bring this Xcode capability back!!! Losing this feature introduces immense cognitive overhead in the development, design, and maintenance of a Core Data data model. The best analogy that I can come up with for this backwards move, is that it's the same as asking Mac users to give the GUI they overwhelming love and appreciate, and force them to revert back to using the command line.