You can't really save it in the way you're imagining, but if you click on the "history" tab it will show your previous searches, maybe even 20 or more of them. It's easy to choose one, pull it up and tweak it from there. I'm sorry I can't help on the tracker app...didn't even know it existed until now.
I don't know if this will help you or not, but I have two trips I track all the time, in both directions. So I just keep two open tabs in my browser--one for each of the trips--and tweak or reverse each as necessary.