How to hide node/add and */edit page titles
Try with hook_preprocess_page_title

function myModule_preprocess_page_title(&amp;$variables) {
  //- Get the Current route name 
  $route_name = \Drupal::routeMatch()-&gt;getRouteName();
  switch ($route_name) {
    //- Add node Page
    case 'node.add' :
      $variables['title'] = t('New add page title');
      break;
    //- Edit node Page
    case 'entity.node.edit_form' :
      $variables['title'] = t('test');
      break;
  }
}