code: public function handle(EncodePropertyValueFromWidgetEvent $event)
      {
          if (('tl_metamodel_dca_combine' !== $event->getEnvironment()->getDataDefinition()->getName())
              || ('rows' !== $event->getProperty())) {
              return;
          }
  
          $values = $event->getValue();
          $index  = 0;
          $time   = time();
          foreach (array_keys($values) as $key) {
              $values[$key]['sorting'] = $index;
              $values[$key]['tstamp']  = $time;
  
              $index += 128;
          }
  
          $event->setValue($values);
      }
docs: Handle event to update the sorting for DCA combinations.
  
  @param EncodePropertyValueFromWidgetEvent $event The event.
  
  @return void