TestLocalAction4.php

<?php

namespace Drupal\menu_test\Plugin\Menu\LocalAction;

use Drupal\Core\Menu\LocalActionDefault;
use Drupal\Core\StringTranslation\StringTranslationTrait;
use Symfony\Component\HttpFoundation\Request;

/**
 * Defines a local action plugin with a dynamic title.
 */
class TestLocalAction4 extends LocalActionDefault {
    use StringTranslationTrait;
    
    /**
     * {@inheritdoc}
     */
    public function getTitle(Request $request = NULL) {
        return $this->t('My @arg action', [
            '@arg' => 'dynamic-title',
        ]);
    }

}