Highcharts: structure legend by subtitles

I was playing around with Highcharts the last days.

One thing, I couldn't find out, is if it is possible to include subtitles to the legend to structure the results.

In my example: http://jsfiddle.net/gWEtB/

var allData={
        products: ["Product1", "Product2", "Product3", "Product4"]
    }

var colors={
        'own': ['#3B14AF', '#422C83', '#210672', '#886ED7'],
        'comp': ['#E7003E', '#AD2B4E',  '#960028',  '#F33D6E',  '#F36D91'],
        'new':  '#00CC00'}

`$(function () {
    $('#container').highcharts({
        chart: {
            type: 'column'
        },
        title: {
            text: 'Product Switching'
        },
        xAxis: {
            categories: allData.products
        },
        yAxis: {
            min: 0,
            title: {
                text: ''
            },
            labels:{ 
                format:'{value} %'
            }
        },
        tooltip: {
            pointFormat: '<span style="color:{series.color}">{series.name}</span>: <b>{point.percentage:.0f}%</b><br/>',
            shared: false
        },
        plotOptions: {
            column: {
                stacking: 'percent',
                dataLabels: {
                    enabled: true,
                    formatter: function(){
                        return this.percentage.toFixed(2)+' %';
                    },
                    color:'#FBF5EF'
                }
            }
        },
        legend: {
            layout: 'vertical',
            align: 'right',
            verticalAlign: 'top',
            y: 30,
        },
            series: [{
            name: 'Own product1',
            data: [5, 3, 4, 7],
            color: colors.own[0]
        },
        {
            name: 'Own product2',
            data: [5, 3, 4, 7],
            color: colors.own[1]
        }, 
        {
            name: 'Own product3',
            data: [5, 3, 4, 7],
            color: colors.own[2]
        }, 
        {
            name: 'Own product4',
            data: [5, 3, 4, 7],
            color: colors.own[3]
        }, 
        {
            name: 'Competitor 1',
            data: [2, 2, 3, 2],
            color: colors.comp[0]
        },
        {   
            name: 'Competitor 2',
            data: [2, 2, 3, 2],
            color: colors.comp[1]
        },
        {
            name: 'Competitor 3',
            data: [2, 2, 3, 2],
            color: colors.comp[2]
        },
        {
            name: 'Competitor 4',
            data: [2, 2, 3, 2],
            color: colors.comp[3]
        },
        {
            name: 'Competitor 5',
            data: [2, 2, 3, 2],
            color: colors.comp[4]
        },          {
            name: 'Market Potential',
            data: [3, 4, 4, 2],
            color: colors.new
        }]
    });
});

I look for a way to add subtitles to the legend in this way:

Cannibalization:
o Own product 1
o Own product 2
o Own product 3
o Own product 4

Competition:
o Competitor 1
o Competitor 2
o ...

I am thankful for all help and information.

thx

You can use labelFormatter http://api.highcharts.com/highcharts#legend.labelFormatter

Simple example: http://jsfiddle.net/gWEtB/1/

labelFormatter: function() {
                switch(this.name)
                {
                    case 'Own product1':
                        return 'Cannibalization<br/>'+ this.name;
                        break;
                    case 'Competitor 1':
                        return this.name + '<br/>Competition';
                        break;
                     case 'Market Potential':
                        return this.name + '<br/>Market title';
                        break;
                    default:
                        return this.name;
                        break;
                }

            }