I'm not sure what you wanted to be added. When the airplane is flagged as Cargo, the following will change:
- Instead of passengers stairs, Cargo stairs with a more industrial look will be used.
- Instead of passengers and crew, you'll se only Pilots and a Loadmaster, the guy with a notebook in his hand.
Those are the things that will change, because of that option.
To SEE the high loader loading pallets, it requires to have the Main Cargo door properly configured, that's is unrelated to the "Cargo" option, which only changes the stairs and the crew.
As confirmed multiple times, the official configurations for all the 737-800 variants are coming very soon, possibly today (depends how many forum post I need to answer about them)