[Solved]-Is there a way to add a custom tooltip to the second level columns of the drilldown on highcharts?-Highcharts

You can achieve it using tooltip.formatter and additional property saved in the point object. Check demo and code posted below.

Code:

tooltip: {
  formatter: function() {
    if (this.point.tooltipInfo) {
      return 'Something: <br>- ' + this.point.tooltipInfo.join('<br>- ');
    }

    return this.y;
  }
},
drilldown: {
  series: [{
    name: "Category 1",
    id: "cat1",
    data: [{
        name: "stuff 1",
        y: 4,
        tooltipInfo: ['aaa', 'bbb', 'ccc', 'ddd']
      },
      {
        name: "stuff 2",
        y: 6,
        tooltipInfo: ['aaa', 'bbb', 'ccc', 'ddd', 'eee', 'fff']
      },
      [
        "stuff 3",
        5
      ],
      [
        "stuff 4",
        6
      ]
    ]
  }]
}

Demo:

• http://jsfiddle.net/BlackLabel/vjoprc7t/

API reference:

• https://api.highcharts.com/highcharts/tooltip.formatter