While doing the refactoring I found my editor would no longer launch.
I had actually heard this somewhere (possibly in this course, maybe somewhere else) that selecting “Product > Clean” from inside Xcode deletes the UE4 Editor.
The error was obscure - you just can’t launch the UE 4 environment by double-clicking the EscapeRoom.uproject file. And trying to run it from the launcher gets an obscure error message. Eventually discovered the “Verify” option as per the a forum post. From “Epic Games Launcher”:
