@Joel B. Mohler as mentioned, there is no central place to do this, but I find "Customization > Scripting > Scripted Recrods" extremely helpful at determining what is running on each record. This could be run through and documented. I highly recommend documenting any customization when they are built and trying to update them as you go, but if they are already made, then you need someone to go through it and document. Good luck!