bug filed as FB15425116 thanks Quinn for confirming my thoughts.

I have written a CoreData model visualisation tool. Just released on the App Store : https://apps.apple.com/us/app/coredata-model-editor/id6449733666 So far, it is just a graphical view of the model, but it updates everytime you save your modification in XCode. So you can have XCode on one half of yoru screen and edit your model with tables, and immediately see the graphic view when you save. I'll turn the app into a real editor as soon as possible. I hope that helps...