You can add a waypoint to a flight plan by clicking anywhere on the map. Flightplan will drop a push-pin at the coordinate you clicked, and open the Add Waypoint form (see below). You can update the waypoint ID which will show in the glass cockpit if your aircraft is so equipped. You can also set your preferred description and altitude in feet (FT) or meters (M).
Check out the video above to learn how, as well as the other videos in our How To playlist on YouTube at https://youtube.com/@Simflightplan