Learning about other ppx transformations with ppxlib

According to ppxlib’s tutorial, it is possible to write “more advance transformations” in addition to derivers and extension rewriters:

It is also possible to write more advanced transformations such as rewriting constants that bear the right suffix, rewriting function calls based on the function identifier or to generate code from items annotated with a custom attribute but we won’t cover those in this section.

Is there any place where I can read about implementing these kind of transformations? Any code example? Any software using these features?