I think there have been a few posts on this that I remember seeing but, I couldn't find the exact one.
The important thing to remember is that grills that use the small propane canisters will have a regulator. The quick disconnect line is already regulated as it is fed from the onboard propane tanks.
Some grills you can remove the regulator. If you can't remove the regulator you will need to somehow install another control valve for the grill.
Basically you will need the following:
2. Camco 57280 39" RV Quick-Connect to Quick-Connect LP Gas Hose : Amazon.com : Automotive
The gas control knob will control the gas flow without using the regulator and the extension line is just that. It will get your line from the camper further away.
Obviously, I don't know your exact setup but, that might get you closer to the ballpark. The main thing is that your grill has a regulator on it most likely and the quick disconnect line is already regulated. Another way to think of it is that the grill is high pressure and the quick disconnect is low pressure.
Hope it helps somewhat.