Yeah that. You can add whatever you want or edit or even extend some limits through the xml files, and for what he did was ok because there was no need for any internal ids, but as you can see he's hit his own roadblock with that.
The file I speak of though is not an xml file but an sod file, but still you can add stuff there, if you know the internal ids.
I suppose though if you truly want to know the extent of what can and can't be edited, look in the xml files.
I only found .txt files, where would this XML files be?
