[Solved]-Highcharts custom formatting/coloring of category labels-Highcharts

To increase the width, you can set width style:

yAxis: {
    labels: {
        useHTML: true,
        style: {
            width: '300px',
            textOverflow: 'ellipsis'
        }
    },
    ...
},

Live demo: https://jsfiddle.net/BlackLabel/nkz9xmh0/

API Reference: https://api.highcharts.com/gantt/yAxis.labels.style