如果您想根据标签长度和相对于图表宽度来设置标签宽度，您可以使用chart.event.render来实现。它将允许您找到字符数并动态设置百分比宽度。

var allowChartUpdate = true;

Highcharts.chart('container', {

  chart: {
    type: 'bar',
    styledMode: true,
    events: {
      render: function() {
        if (allowChartUpdate) {
          this.xAxis[0].categories.forEach(category => {
            if (category.length > 10) {
              var dynamicMargin = this.chartWidth * 50 / 100;
              allowChartUpdate = false;

              this.update({
                chart: {
                  marginLeft: dynamicMargin
                }
              }, true, true, false);

              allowChartUpdate = true;
            }
          })
        }
      }
    }
  },
...

示范：

https://jsfiddle.net/BlackLabel/59xjq4du/

API参考：

https://api.highcharts.com/highcharts/chart.events.render