[Solved]-HighStock: Loading series data asynchronously as needed-Highcharts

You are looking for the xAxis.events.setExtremes event.

You will need to combine it with Series.addPoint(Object options, [Boolean redraw], [Boolean shift], [Mixed animation]) inside a loop with the redraw option as false inside the it and explicitly call Chart.redraw() after looping all the newly added points.

You may also need to look @ navigator.series since your navigator series may require to be different from the actual series