The easiest way I know to find a transfer switch is to trace the shore power cord into the coach. If you have a transfer switch, the shore power cord will originate (terminate?) there because that's where the "decision" is made to use shore power or generator power.
Denny, Connie & Shadow (former barn cat made good)
2000 Itasca Horizon, Cat 3126B, Freightliner Chassis