The only other adjustment is turning off the rear PDC. You can check if that functions as designed quite easily, by putting it in reverse with the trailer connected.

There is a trailer stability control mode in the DSC program, but that wouldn't depend on bulb warning lights IMO.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue