Hey,
You can store the chart.savedAnnotationIcons array in the
localStorage and then on the chart.events.load, if there is any, get the data from localStorage and render that using the renderAnnotation method.
Or you can store this data on your server and then also fetch it in the load event so that you can render the annotations.
In case of any other questions related to Highcharts functionality feel free to contact us anytime
Best regards
Jakub