anchor property
The anchor the step is placed at, by name: one of the engine's
(after bloom), or one another plugin added to the renderer
(RendererSteps.addAnchor). A name, not a RenderAnchor, because a
plugin's anchor is the renderer's, and the document is read before
there is one; it is resolved with RendererSteps.anchorNamed when the
plugin is installed.
Implementation
final String anchor;