ORIGIN AND DESTINATION ENTRY FOR FLIGHT PLANS

[McCloud9]

Why does the GTNXi always default to Waypoint or add a waypoint instead of starting at Origin first so I can enter the airport taking off from, then destination so I can add where I am flying to, THEN add waypoints? I never see Origin and destination entries only add waypoints, very frustrating. 

All I ever see, even when starting from a new flight plan is "Add Waypoint".  Also for some reason, I have ran into a number of airports in MSFS that are not in the GTNXi 750 database.  Any help appreciated.

Thank you 

Don