There is no script command to create a waypoint, aside from the "move" command. However, what you could do is to create the unit in a group that you place in the editor that has a S&D waypoint.
Place a guy in the editor, and put "group1=group this; deletevehicle this"; in the units init field. Then give him a S&D waypoint. When you create your unit via scripting, make him start as part of group1. He should then proceed to the groups waypoint.