spacing property
The distance between the outer edge of the chart and the content, like title or legend, or axis title and labels if present. The numbers in the array designate top, right, bottom and left respectively. Use the options spacingTop, spacingRight, spacingBottom and spacingLeft options for shorthand setting of one option.
API Docs: https://api.highcharts.com/highcharts/chart.spacing
Implementation
List<double>? spacing;