getBlockLinks example

$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;
      $block_categories[$category]['#title'] = $category;
      $block_categories[$category]['links'] = $this->getBlockLinks($section_storage, $delta, $region, $blocks);
    }
    $build['block_categories'] = $block_categories;
    return $build;
  }

  /** * Provides the UI for choosing a new inline block. * * @param \Drupal\layout_builder\SectionStorageInterface $section_storage * The section storage. * @param int $delta * The delta of the section to splice. * @param string $region * The region the block is going in. * * @return array * A render array. */