The only command I couldn't find was that to create a new waypoint.
You don't need to create waypoints, each single unit (un-grouped) or a group leader get's a initial waypoint right on top of it.
It's number is 0 and you can access it with the new waypoint commands.
For example
[groupname,0] setWaypointBehaviour "safe"
EDIT:
Oh, and the command for creating waypoints is
addWaypointBut I don't think that's what Dj Tano is after
You mean setting a trigger in the editor?
If so, set the triggers type to 'switch' and synchronize the trigger with a waypoint prior to the waypoint you want the unit to go to.
Once the trigger gets activated it will 'free' the next waypoint for the unit..