variableAnchors

Provide anchor choices for annotation placement. The first anchor in the list that allows the view annotation to be placed in the view is picked. If the array is empty, the default `ViewAnnotationAnchorConfig` value will be applied. When adding new annotations, if `variableAnchor` is not explicitly set, the default `ViewAnnotationAnchorConfig` value will be applied. When updating existing annotations, if `variableAnchor` is not explicitly set, the current value will be retained.