add(new AjaxButton("submit") {
@Override
protected void onSubmit(AjaxRequestTarget target, Form<?> form) {
AbstractContainer node = (AbstractContainer) VariablesPanel.this.getModelObject();
node.setVariableValue(key, value);
node.save();
onItemAdded();
key = null;
value = null;
target.addComponent(form);
target.addChildren(findParent(VariablesPanel.class), FeedbackPanel.class);