I used the export to GPX function provided in the screen that comes up when you are viewing the Results (on the Optimise ribbon) and have then selected one of the routes that has been generated to see further details. The results were generate using the Ensemble function so there is a route for each grib. 

Thanks Campbell. I was expecting it to come up as a track so wasn’t looking in the Marks folder.  I am away from a computer where I can check this out but will give it a go in a week when I am back. 

in older versions there was a button "export to marks" in the result window showing the optimal route, then the route came up immediately in the marks/route database as a route. How does that work now ? I tried export to gpx file, then all optimal route marks come up as separate marks (each in one dedicated mark folder), it is not practical to then build the route. Or I tried export to gpx trk file, then the optimal route name is in the route window, but empty (without marks). The manual says simply the optimal route can be exported to the mark database, but not how.

sorry, but could you post how the optimal route must be exported and then imported to mark folder, I cannot get any satisfactory result.