removeButtonSubmit example

    $triggering_element = $form_state->getTriggeringElement();
    $delta = array_slice($triggering_element['#array_parents'], -2, 1)[0];

    /** @var \Drupal\media\MediaInterface $removed_media */
    $removed_media = $form_state->get(['media', $delta]);

    $file = $removed_media->get($this->getSourceFieldName($removed_media->bundle->entity))->entity;
    if ($file instanceof FileInterface && empty($this->fileUsage->listUsage($file))) {
      $file->delete();
    }

    parent::removeButtonSubmit($form, $form_state);
  }

}