JavaFX CSS for nested SplitPanes - css

Question

I'm tasked with styling/skinning a JavaFX application. I'm trying to do as much in CSS stylesheets as possible rather than in the code. I've got a question about nested SplitPanes: when the application is rendered, is there anything that is created surrounding the inner SplitPane that gets in between the outer SplitPane and the inner SplitPane in the parent/child hierarchy of nodes.
Here's a little test application that mimics my full application:
BorderPane root = new BorderPane();
root.setId("root");
Label mws_header = new Label("This is the header");
root.setTop(mws_header);
Label sidebar = new Label("This is the sidebar");
root.setLeft(sidebar);
SplitPane outer = new SplitPane();
outer.setId("mws_pano_360_split");
outer.setOrientation(Orientation.VERTICAL);
root.setCenter(outer);
Label bigGraphic = new Label("This is the top");
outer.getItems().add(bigGraphic);
SplitPane inner = new SplitPane();
inner.setId("flat_data_split");
inner.setOrientation(Orientation.HORIZONTAL);
Label label1 = new Label("This is the left");
Label label2 = new Label("This is the right");
inner.getItems().addAll(label1, label2);
outer.getItems().add(inner);
In the CSS, what I'd like to do is get to the inner SplitPane using direct child syntax:
BorderPane > SplitPane > SplitPane {
/* all kinds of styling of background colors */
}
But instead, what I have to do is treat it as a descendant:
BorderPane > SplitPane SplitPane {
/* all kinds of styling of background colors */
}
So what might be getting in between the outer SplitPane and the inner SplitPane? I'd love to have a tool that lets you inspect the parent/child nodes in the hierarchy but so far haven't found one.