checkboxClick property

Fires when the checkbox next to the point name in the legend is clicked. One parameter, event, is passed to the function. The state of the checkbox is found by event.checked. The checked item is found by event.item. Return false to prevent the default action which is to toggle the select state of the series.

API Docs: https://api.highcharts.com/highcharts/series.variablepie.events.checkboxClick