Where to Plug In Emergency Stop Button aka latest Machine Documentation caught lacking

I have the Ray, Enclosure, Air Purifier and the Rotary module. Where does the emergency stop button go? Where does it plug in if all of the other CAN ports are used? Can I use the CAN hub? I am disappointed in the documentation on the Ray as it is only online and incomplete and confusing. The original printed documentation that came with the A350T, Enclosure and everything was great and comprehensive. The documentation for the Ray being in the wiki is incomplete and confusing.

Can hub is a simple pcb, it should work anyway.