Welcome to our forum & thanks for the question!
Currently, there's no option that you can add to the config to achieve this. However, you can easily render a custom label on the plotLine using the Highcharts.SVGRenderer
With our SVGRenderer you can render custom SVG elements such as: texts, labels, rectangles, circles, custom shapes (literally anything that you can draw as an SVG).
Usually, we do it like this:
1. Use the chart.events.render
event which is triggered after each chart render.
2. If the custom element has already been rendered it means that it's not the first render of the chart; thus, we only need to reposition it correctly as the dimensions of the chart might have changed.
3. If the custom element has not been rendered it means that it is the first render of the chart; thus, we have to render it for the first time with the Highcharts.SVGRenderer.
Here's a demo: https://jsfiddle.net/BlackLabel/oyjd7xz2/
You can style this label as you wish with the .attr()
methods which exist on the Highcharts.SVGElement.
Please let me know if that helps.