@Nullable
      @Override
      protected Transferable createTransferable(JComponent c) {
        final Object selection = tree.getLastSelectedPathComponent();
        if (!(selection instanceof DefaultMutableTreeNode node)) {
          return null;
        }
        if (!(node.getUserObject() instanceof Configuration)) {
          return null;
        }
        return new TextTransferable(ConfigurationUtil.toXml((Configuration)node.getUserObject()));
      }
@Nullable
      @Override
      protected Transferable createTransferable(JComponent c)