We encountered the same question when we purchased our used 5er. Turned out the two switches did nothing because they controlled a "scare" exterior light on each side of the unit, and both lights had burned out bulbs. Usually, switches just inside the entry door are for exterior lights, porch light, or an overhead interior entryway light. One other possibility is a coat closet inside light, if you have one. Other than that, I don't have any other ideas. You could also contact Jayco via email, with the VIN number of your trailer, and query them.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, Teddy (Jack Russell terrier), and Honey (Beagle)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.