relativeTo property
What coordinate system the field and borderPath should relate to.
If plotBox, they will be fixed to the plot box and responsively
move in relation to the main map. If mapBoundingBox, they will be
fixed to the map bounding box, which is constant and centered in
different chart sizes and ratios.
API Docs: https://api.highcharts.com/highcharts/mapView.insetOptions.relativeTo
Implementation
String? relativeTo;