NSTableView.DraggingDestinationFeedbackStyle.gap
Provides a gap insertion when dragging over the table. Note that this style is only officially supported for Nsview-based table views, but may partially work in Cell Based TableViews. The decision to use the gap style (compared to another style) can be made in Tableview(_:draggingsession:willbeginat:forrowindexes:), or it can dynamically be changed.
Declaration
case gap