Hello Prajjwal,
Welcome to our forum and thanks for contacting us with your question!
Unfortunatelly it is not possible to add such shape purely from API. There are few options that you might want to consider though.
First and probably most consistent one is to change dumbbell markers based on the trend. You can do it with option such as
marker.shape and
marker.fillColor.
Demo:https://jsfiddle.net/BlackLabel/yt6hf1b0/
API reference: https://api.highcharts.com/highstock/se ... ker.symbol,
https://api.highcharts.com/highstock/se ... .fillColor
Second option is to add second scatter series which would overlap with dumbbell showing the trend.
Demo: https://jsfiddle.net/BlackLabel/tv1p9e5c/
Last option is to use SVGRenderer which allows you to draw custom shapes on the chart. This is a good option too but will most likely require more work than previous two because you have to find right positions based on the points to render custom shapes.
API reference:https://api.highcharts.com/class-refere ... VGRenderer
Let me know if that was what you were looking for!
Best regards!