After following this topic and filtering through Barry's nonsense I was able to write my little app in just 3 hours.
Congratulations!Summary of topic as I read it:
1. You can save files to the engine folder during a build, but the engine folder is read-only when run on a device.
2. f you want to save app or user data, use the Documents folder at specialFolderPath("documents"). Note it is case-sensitive. Documents is read/write and is intended for your own files.
I think that's the bare bones of the thread. Pretty simple really.
Barry: it doesn't matter what file path Documents is mapped to, and you can ignore the developer ID, it has no significance for your scripts. The engine uses a virtual mapping scheme, and if Android changes the mapping may change later anyway. Just use specialFolderPath, which will always point to the right location and let the engine work out the details for you.