The code sample underneath demonstrates the issue. Subnodes of a CustomNode can not be looked up.

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Product Version: NetBeans IDE 6.8 (Build 200912041610)
Java: 1.6.0_17; Java HotSpot(TM) 64-Bit Server VM 14.3-b01
System: Linux version 2.6.31-16-generic running on amd64; UTF-8; en_US (nb)
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import javafx.scene.CustomNode;
import javafx.scene.Node;
import javafx.scene.text.Text;
import javafx.scene.Group;

class Test extends CustomNode {

    def one = Text {
        id: "one"
    }

    def two = Text {
        id: "two"
    }

    def three = Text {
        id: "three"
    }


    def group = Group {
        content: [ one, two, three ]
    }

    override protected function create () : Node {
        group;
    }
}

def node = Test{};

// returns null
def lu = node.lookup("two");

println("Looked up object {lu}");