To determine if you really need to do anything, try towing the trailer with the "full" WD setup, but with empty tanks. You're not going to hurt a thing by trying. Worst case you won't like the way it rides. That'd be the only reason to change the settings.
If you do feel you need to have a second setup for "empty," then go through the setup process. The difference will likely only be one link in the chains, as mentioned previously.
The people I camp with don't change the settings on their WD hitches to go home, even after emptying their fresh tanks before leaving.
