https://api.drupal.org/api/drupal/core%21modules%21layout_builder%21src%21Controller%21AddSectionController.php/8.9.x
AddSectionController.php | Drupal API
phpdrupalapi
https://api.drupal.org/api/drupal/core%21modules%21layout_builder%21src%21Controller%21AddSectionController.php/function/AddSectionController%3A%3Acreate/10
function AddSectionController::create | Drupal API
functioncreatedrupalapi