This may be obvious to everyone, but I developed roundtrip B-52 navigation from takeoff to a target and then return to takeoff airport this way.  My destination for a B-52 flight was Havana,
Cuba, from Tinker AFB.  I wanted to program a roundtrip back to Tinker, but the FSX flight planner doesn't permit this.  I set the flight plan from Tinker to a checkpoint in Cuba and then back to an airport near Tinker.  This flightplan included Tinker as a checkpoint on the way back to the destination near Tinker. I simpy flew to the Tinker checkpint as a destination rather than checkpoint and then flew the approach to Tinker.