overscroll property

Additional range on the right side of the xAxis. Works similar to xAxis.maxPadding, but the value is set in terms of axis values, percentage or pixels.

If it's a number, it is interpreted as axis values, which in a datetime axis equals milliseconds.

If it's a percentage string, is interpreted as percentages of the axis length. An overscroll of 50% will make a 100px axis 50px longer.

If it's a pixel string, it is interpreted as a fixed pixel value, but limited to 90% of the axis length.

If it's undefined, the value is inherited from xAxis.overscroll.

Can be set for both, main xAxis and navigator's xAxis.

API Docs: https://api.highcharts.com/highcharts/navigator.xAxis.overscroll