Is it possible to add a custom symbol in a line chart? 

Just like in this example:

In the example, custom symbols are set in 'series' array in HighChart options.

I can't find a way to use DataPoint structure to show custom symbols.

The datapoints are shown in your current chart?  

Hi Yosuke,

Yes, it's possible.

You need to use an action called AdvancedFormatInit, and set the JSON properties that you want. Then pass it to the chart.

You have a great component here that will help you understand how to achieve it.