Would you like to change the legend during export? I.e Have latin characters in the chart, and change them to arabic during exporting?

If yes, then you are using built-in exporting options, here is the API option to update the chart just for exporting: https://api.highcharts.com/highcharts/exporting.chartOptions

Additionally, have a look at the internationalization page in the docs with Arabic chart included: https://www.highcharts.com/docs/advanced-chart-features/internationalization