How can I record a route in several stages?

If you want to undertake a multi-day route and record it as a single trail, one way to do it is to save the journey in draft mode:

After recording a stage, press the stop button.
Select Finish and, at the bottom of the screen, choose Save as draft. This will allow you to continue recording later.
To resume recording, go to the Profile tab, select Your trails, and choose the draft trail highlighted in orange. The trail will reactivate in the Record trail tab.
Remember, if the starting point differs from where you last finished, the app will ask you to move closer to that last point; otherwise, it will draw a straight line between the two points on the map.

It is important not to log out or uninstall the app while the route is saved as a draft, as you would lose all unsaved information.