Currently, the CA TPX user macros are in related topics in TPX Programming, mainly in Setting Up User Exits.
https://docops.ca.com/ca-tpx-session-management/5-4/en/programming/tpx-programming/setting-up-user-exits
Your idea of central topic for all user exposed macros is being reviewed and we plan to implement that in a phased approach. No timeframe as yet.
In the meantime, for specific problems or general assistance in creating your exit, please contact CA Support and we can assist. While Support cannot write nor support a custom exit, we may be able to provide direction and technical information from Sustaining Engineering.