private void create(String treeName) {
		setLayout(new BorderLayout());
		ProgramNode root = null;

		root = new ProgramNode(null, "No Program");

		treeModel = new DefaultTreeModel(root);
		tree = new ProgramDnDTree(treeName, treeModel, plugin);

		scrollp = new JScrollPane(tree);
		scrollp.setPreferredSize(new Dimension(300, 300));

		add(scrollp, BorderLayout.CENTER);

		// add change listener on viewport to know when the pageDown
		// key is hit; see the stateChanged() method.
		scrollp.getViewport().addChangeListener(this);

		setFocusable(false);
	}
Create a new TreeModel and add it to this panel.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/programtree/ProgramTreePanel.java