code: public function handle(GetOptionsEvent $event)
      {
          if (('tl_metamodel_dca_combine' !== $event->getEnvironment()->getDataDefinition()->getName())
              || ('rows' !== $event->getPropertyName())
              || ('dca_id' !== $event->getSubPropertyName())) {
              return;
          }
  
          $screens = $this
              ->connection
              ->createQueryBuilder()
              ->select('id')
              ->addSelect('name')
              ->from('tl_metamodel_dca')
              ->where('pid=:pid')
              ->setParameter('pid', $event->getModel()->getProperty('id'))
              ->execute()
              ->fetchAll(\PDO::FETCH_ASSOC);
  
          $result = [];
          foreach ($screens as $screen) {
              $result[$screen['id']] = $screen['name'];
          }
  
          $event->setOptions($result);
      }
docs: Get all options for the input screens.
  
  @param GetOptionsEvent $event The event.
  
  @return void