[Solved]-Highcharts tooltip for single series always centre. Can I force it to be left hover of the marker?-Highcharts

You can use the tooltip.positioner callback to achieve the desired effect.

Demo: https://jsfiddle.net/BlackLabel/9of37Lyx/

tooltip: {
    shared: true,
    positioner(labelWidth, labelHeight, point) {
      return {x: point.plotX - labelWidth / 2, y: point.plotY}
    }
},

API: https://api.highcharts.com/highcharts/tooltip.positioner