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Sorry I can't give you an exact answer to you question , but many inverters would automatically by-pass once shore power is established, no need to turn them off .
Because part of the inverter function when on shore power , would be to charge the coach batteries.
I would think the switch would be to switch the inverter off when the coach is not being used to avoid running the battery down.
A couple of things to confirm this ( if no member with a similar unit can give the answer) would be a picture of the switch and the make and model of the inverter.