Hello semrola,
Thanks for contacting us with your question.
Unfortunately something like that is not supported and you can't do it purely with API options. You could use SVGRenderer which allows you to draw text on your chat. Finding right label position might be hard though.
Demo: https://jsfiddle.net/BlackLabel/r0u5fg6c/
API reference: https://api.highcharts.com/class-refere ... VGRenderer
Let me know if you have any further questions!
Best regards!