NavigationTestBlockHooks.php

<?php

declare (strict_types=1);
namespace Drupal\navigation_test_block\Hook;

use Drupal\Core\Hook\Attribute\Hook;

/**
 * Hooks implementations for navigation_test_block module.
 */
class NavigationTestBlockHooks {
    
    /**
     * Implements hook_block_alter().
     */
    public function blockAlter(&$definitions) : void {
        $definitions['navigation_test']['allow_in_navigation'] = TRUE;
    }
    
    /**
     * Implements hook_navigation_defaults().
     */
    public function navigationDefaults() : array {
        $blocks = [];
        $blocks[] = [
            'delta' => 1,
            'configuration' => [
                'id' => 'navigation_test',
                'label' => 'My test block',
                'label_display' => 1,
                'provider' => 'navigation_test_block',
            ],
        ];
        return $blocks;
    }

}