Highcharts - Getting a 3d effect with selected pie chart slices

To achieve extra border when you hovering you can trigger to the point.events and add SVG attributes.

  plotOptions: {
    pie: {
      type: 'pie',
      innerSize: '80%',
      allowPointSelect: true,
      slicedOffset: 0,
      states: {
        hover: {
          halo: null,
          brightness: 0,
        },
      },
      point: {
        events: {
          mouseOver: (obj) => {
            obj.target.graphic.attr({
                'stroke-width': 50,
                stroke: obj.target.color,
                zIndex: 3,
                filter: 'drop-shadow(0 0 10px black)'
              }).css({
                borderRadius: 20
              })
              .add();
          },
          mouseOut: (obj) => {
            obj.target.graphic.attr({
                'stroke-width': 1,
                stroke: obj.target.color,
                filter: 'transparent'
              }).css({
                borderRadius: 0
              })
              .add();
          },
        }
      }

    }
  },

Live demo:

https://jsfiddle.net/BlackLabel/u4ypbsrk/

API References:

https://api.highcharts.com/class-reference/Highcharts.SVGElement#attr,

https://api.highcharts.com/class-reference/Highcharts.CSSObject,

https://api.highcharts.com/highcharts/plotOptions.pie.point.events