Once you have saved your original trip, you can go to the Wrench Icon in your Trip Settings (upper left), and copy your trip. When you do that copy, you can name the copy however you want and use it for your alternate planning trip. Once saved, neither trip is a sub to the other, they are independent trips. So if you make changes to the copy you are experimenting with and like the result, you'll have to manually add those specific changes to your baseline trip. Many RVTW users do this as it's an excellent way to optimize your trip, and add/subtract as you discover new info.
Mike and Cindy
2016 Tiffin Allegro Open Road 34PA
2010 Pontiac G6