blockAddHighlightId example

'#size' => 30,
      '#placeholder' => $this->t('Filter by block name'),
      '#attributes' => [
        'class' => ['js-layout-builder-filter'],
        'title' => $this->t('Enter a part of the block name to filter by.'),
      ],
    ];

    $block_categories['#type'] = 'container';
    $block_categories['#attributes']['class'][] = 'block-categories';
    $block_categories['#attributes']['class'][] = 'js-layout-builder-categories';
    $block_categories['#attributes']['data-layout-builder-target-highlight-id'] = $this->blockAddHighlightId($delta, $region);

    $definitions = $this->blockManager->getFilteredDefinitions('layout_builder', $this->getPopulatedContexts($section_storage), [
      'section_storage' => $section_storage,
      'delta' => $delta,
      'region' => $region,
    ]);
    $grouped_definitions = $this->blockManager->getGroupedDefinitions($definitions);
    foreach ($grouped_definitions as $category => $blocks) {
      $block_categories[$category]['#type'] = 'details';
      $block_categories[$category]['#attributes']['class'][] = 'js-layout-builder-category';
      $block_categories[$category]['#open'] = TRUE;
      

'layout-builder__link--add',
              ],
              'data-dialog-type' => 'dialog',
              'data-dialog-renderer' => 'off_canvas',
            ],
          ]
        ),
      ];
      $build[$region]['layout_builder_add_block']['#type'] = 'container';
      $build[$region]['layout_builder_add_block']['#attributes'] = [
        'class' => ['layout-builder__add-block'],
        'data-layout-builder-highlight-id' => $this->blockAddHighlightId($delta, $region),
      ];
      $build[$region]['layout_builder_add_block']['#weight'] = 1000;
      $build[$region]['#attributes']['data-region'] = $region;
      $build[$region]['#attributes']['class'][] = 'layout-builder__region';
      $build[$region]['#attributes']['class'][] = 'js-layout-builder-region';
      $build[$region]['#attributes']['role'] = 'group';
      $build[$region]['#attributes']['aria-label'] = $this->t('@region region in @section', [
        '@region' => $info['label'],
        '@section' => $section_label,
      ]);

      

  public function buildForm(array $form, FormStateInterface $form_state, SectionStorageInterface $section_storage = NULL, $delta = NULL, $region = NULL, $plugin_id = NULL) {
    // Only generate a new component once per form submission.     if (!$component = $form_state->get('layout_builder__component')) {
      $component = new SectionComponent($this->uuidGenerator->generate(), $region, ['id' => $plugin_id]);
      $section_storage->getSection($delta)->appendComponent($component);
      $form_state->set('layout_builder__component', $component);
    }
    $form['#attributes']['data-layout-builder-target-highlight-id'] = $this->blockAddHighlightId($delta, $region);
    return $this->doBuildForm($form, $form_state, $section_storage, $delta, $component);
  }

}