Mouse events are defined in the File Types UI because you can make them do different things for different file types (and folders). In this case you only have to change the one event, on the All Folders type.
You don't need to edit any oxr files.
You can make the middle double-click events trigger on single click by changing a Preferences setting.
The two steps needed to do this in Opus Pro were described in my earlier reply in this thread and in your other thread:
That's all you need!