[Solved]-How to add markers to a grouped bar plot in Highcharts?-Highcharts

Set x value for the point. By default x values for the scatter are integers - 0, 1, 2 so they are centered according to the category. You can move them a little by 0.15 and then in the pointFormatter round those values.

    series: [{
  name: '2015',
  data: [7, 8, 9]
}, {
  name: '2015 Goal',
  marker: {
    symbol: 'circle'
  },
  data: [
    [-0.15, 5],
    [1 - 0.15, 6],
    [2 - 0.15, 6]
  ],
  type: 'scatter'
}, {
  name: '2016',
  data: [9, 9, 10]
}, {
  name: '2016 Goal',
  marker: {
    symbol: 'circle'
  },
  data: [
    [0.15, 10],
    [1 + 0.15, 12],
    [2 + 0.15, 13]
  ],
  type: 'scatter'
}]

In pointFormatter:

    plotOptions: {
  scatter: {
    tooltip: {
      pointFormatter: function() {
        return `x: <b>${Math.round(this.x)}</b><br/>y: <b>${this.y}</b><br/>`
      }
    }
  }
},

example: http://jsfiddle.net/kh8b4jy3/