[Solved]-Highcharts add single line to column chart-Highcharts

Drawing a custom line is the cleanest solution I guess - you can make that line responsive easily by hooking into redraw event and do re-positioning/resizing.

A series approach doesn't require a lot coding, just setting a few options. You can use a scatter type with a custom marker symbol.

Highcharts.SVGRenderer.prototype.symbols.line = function(x, y, w, h) {
  return ['M', x, y, 'L', x + w, y];
};

{
  type: 'scatter',
  showInLegend: false,
  enableMouseTracking: false,
  marker: {
    symbol: 'line',
    lineColor: 'orange',
    lineWidth: 6,
    radius: 20
  },
  data: [
    [1.15, 140]
  ]
}]

example: http://jsfiddle.net/g6fjjach/