QuickDraw doesn't support combining routes but will hopefully be available in the future. In the meantime, if you need to combine routes and are tech-savvy you can download the map to GPX, manually edit the file to combine any routes you wish, and then import the edited file to create a new map.
You can do this workaround by following these steps:
Via desktop or laptop computer:
- Log on to your account on https://www.alltrails.com
- Export the map as a GPX file by going to 'Plan' in the header and then clicking 'Maps'
- Select the map and then click the 'Download GPX' button
- Open the GPX file in a text editor like Notepad (Windows) or TextEdit (Mac)
- Edit the file to combine routes (see below)
- Save the file when you're done editing it
- Go back to QuickDraw and create a new map
- Simply drag & drop the edited GPX file to import it into your new map