getDefaultPlugin example

$this->entity->removeComponent($field_name);
      $display_options = $this->entity->getComponent($field_name);
    }

    $regions = array_keys($this->getRegions());
    $field_row = [
      '#attributes' => ['class' => ['draggable', 'tabledrag-leaf']],
      '#row_type' => 'field',
      '#region_callback' => [$this, 'getRowRegion'],
      '#js_settings' => [
        'rowHandler' => 'field',
        'defaultPlugin' => $this->getDefaultPlugin($field_definition->getType()),
      ],
      'human_name' => [
        '#plain_text' => $label,
      ],
      'weight' => [
        '#type' => 'textfield',
        '#title' => $this->t('Weight for @title', ['@title' => $label]),
        '#title_display' => 'invisible',
        '#default_value' => $display_options ? $display_options['weight'] : '0',
        '#size' => 3,
        '#attributes' => ['class' => ['field-weight']],
      ],