plugins

// web/modules/contrib/eca/src/Entity/Eca.php (simplified excerpt)

protected function isValidationDisabled(): bool {
  return $this->request()->query->get('eca_validation', '') === 'off';
}

public function getPluginCollections(): array {
  if ($this->isValidationDisabled()) {
    return [];
  }
  // Otherwise every referenced event/condition/action plugin is
  // instantiated here, throwing PluginNotFoundException if one
  // of them no longer exists.
  ...
}

# Delete URL — load this directly, don't click through from a listing page
/admin/config/workflow/eca/{eca_id}/delete?eca_validation=off

\Drupal::service('plugin_id.manager')->clearCachedDefinitions();
// Clear entity_type plugin cache.
\Drupal::entityTypeManager()->clearCachedDefinitions();