Quickstart
See here for the PrefabsV1 API documentation.
It contains both the v1 API usage and how to generally register UIExtenderEx to make it work!
Version 2 of the API builds off of the the concepts of the original API, but offers a bit more versatility, and aggregates some of the original prefab types to offer a (hopefully) simpler API.
All UIExtenderEx patch classes must be flagged with a PrefabExtensionAttribute.
The first parameter is the name of the Movie (the name of the xml file) that your patch targets.
The second parameter is an XPath used to specify the node you wish to target inside of the targetted Movie.
For those of you who are unfamiliar with XPath: