taken from field

Defines whether or not this node's layout will be managed by it's parent. If the node is managed, it's parent will factor the node's geometry into its own preferred size and layoutBounds calculations and will lay it out during the scene's layout pass. If a managed node's layoutBounds changes, it will automatically trigger relayout up the scene-graph to the nearest layout root (which is typically the scene's root node).

If the node is unmanaged, its parent will ignore the child in both preferred size computations and layout. Changes in layoutBounds will not trigger relayout above it. If an unmanaged node is of type Parent, it will act as a "layout root", meaning that calls to Parent.requestLayout() beneath it will cause only the branch rooted by the node to be relayed out, thereby isolating layout changes to that root and below. It's the application's responsibility to set the size and position of an unmanaged node.

By default all nodes are managed.