handleSectionStorage example

    // Mark this as an administrative page for JavaScript ("Back to site" link).     $form['#attached']['drupalSettings']['path']['currentPathIsAdmin'] = TRUE;
    return $form;
  }

  /** * {@inheritdoc} */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $this->handleSectionStorage($this->sectionStorage, $form_state);

    $this->layoutTempstoreRepository->set($this->sectionStorage);

    $form_state->setRedirectUrl($this->getCancelUrl());
  }

  /** * {@inheritdoc} */
  protected function successfulAjaxSubmit(array $form, FormStateInterface $form_state) {
    return $this->rebuildAndClose($this->sectionStorage);
  }