With event.result.node you have an XMLList of the top-level
<node> elements. When you go to <node label="2"
value="b"> it has children which are not flattened into the
Try event.result..node (that is 2 dots) and see if get a
flattened XMLList. If that's the case, then try to use an
itemRenderer for the ComboBox. You'll have to make the itemRenderer
check its data value to see if it has a parent node so you'll know
when to add the "--" before the label.