After you’ve selected the starting and ending points, you can add waypoints anywhere along the trail network as long as it is connected. Hover over the POI icon or simply over the trail network to see the “add a waypoint” button.
Click the button to add the selected point to the route. The route will be adjusted automatically. Waypoints receive numbers and are displayed in the trek builder in the respective order. You can reorder waypoints by moving them up or down while holding the hamburger icon.