In Highcharts currently there is no built-in smoothing option for line charts, but there are ways around it.

1. Have you tried a spline chart? For most use cases, it works well in such a scenario https://www.highcharts.com/docs/chart-and-series-types/spline-chart
2. You can also preprocess your data with a smoothing algorithm like 'moving average', and then use it to plot a chart with Highcharts (line or spline, whatever fits your needs)