Custom Mavlink Mission Command

I have followed this guide to add a custom mavlink message: Adding a new MAVLink Message — Dev documentation

I am trying to create a mission command that has the same functionality as the script_time mission command, however I wish for the argument and timeout to be a static number; not set by the user. I want to create several of these mission commands so it’s easer for the user to setup a mission in the plan tab on MP.

All I’ve done so far is add an entry into the ardupilotmega.XML file for our custom command and I’ve added a case in AP_Mission.cpp’s case statement to handle setting the arguments and timeout to a static number.

I understand I need to build out more of the backend for arriving at the waypoint and handling the timeout, however, I assumed adding the mission to the XML file would allow Mission Planner to find the command and auto populate it by using Ctrl-f → manage command list by typing in the ID, but it doesn’t.

At what point in development will my command show up in Mission Planner or is my logic flawed?