自定义标签
function sumLabel(){
  const point = this;
  const points = point.points;
  const validPoints = points.filter( (point) => point.isVisible() );
  if(point == validPoints[validPoints.length - 1]) //把汇总值显示在第2个系列
  {
    let value = 0;
    for(let i = 0; i < 1; i++)
    {
      value += validPoints[i].value;
    }
    return value;
  } else {
    return "";
  }
}

--
效果
