Did you solve this issue in the end?I have the exactly the same issue with my Reality Composer. I tried editing on my iPad and I was able to add a text, but when I start editing it crashes everytime.I'm desperate to know the solution to it.Thank you very much.

Update: I just went ahead and built&run the app.It worked. I guess it needs to be built once for Xcode to recognize the .swift file.Hopefully it works with you.

I receive the same error as well.It seems like Xcode doesn't recognize the Experience.swift file from the Experience.rcproject file.There were times where I was somehow able to see the Experience.swift as I was toggling through the navigator pane.But I couldn't access it after a couple times, and gave me the same error.Apple, is this a version error?