First of all, my freezer stays frozen when traveling with out connecting to an inverter. But here is how I would do what you want. The inverter usually has two 120V output plugs. Keystone uses on to run the refer. I would intercept the washer/dryer circuit (near the breaker box?), extend it and add a 120V plug, and plug it into the second outlet on the inverter.
Carl (n Susan) Youngren
There is more to life than fuel mileage.
2012 Montana 3700RL Big Sky Package towed by a 2015 Ford F350 6.7L PSD 4WD CC LWB