Good, lacking one key feature

I like this app for browsing weekend hiking possibilities, and plan on using it to track my own trails soon, but I wish it was more interactive. More specifically, Id like to be able to browse through a regional map of trails, and then be able to select different trail routes/ add trail options onto the advertised main trail in the area. It would help me plan if I could add or subtract parts of trails while planing future hikes for myself, and then be able to see the final mileage of your specific route.

Pgp10 about AllTrails: Hike, Bike & Run