On the route selection screen, before you start navigating, you can add a waypoint by tapping the “Add Waypoint” button.
You can select a location by searching on the map or searching through the search engine by entering the address or coordinates.
The order of all selected points on your route, including the starting point and destination, can be adjusted by holding and swiping up/down the = icon on the right side of the selected point finders A B C = start/pass/finish.