Couple different options:
1. If you are using the ShipStation Novemodule integration app, you could modify the mapping a bit for that field and say {{#compare name "===" "Bob"}}"customer id to map"{{/compare}}
2. If using a custom flow, you could do the same or just make a branch in the flow that filters on customer id, email, or whatever. At that point, one branch would be for the specific customer and the other would be to not that customer