Hi Martin,
Reusable Blocks aren’t part of GeneratePress or GenerateBlocks. It’s a WordPress functionality.
One way to add a link to it is through a PHP snippet:
function add_my_reusable() {
global $submenu;
$permalink = admin_url( 'edit.php' ).'?post_type=wp_block';
$submenu['edit.php'][] = array( __('Reusable Blocks'), 'edit_posts', $permalink );
$submenu['edit.php?post_type=page'][] = array( __('Reusable Blocks'), 'edit_posts', $permalink );
}
add_action( 'admin_menu', 'add_my_reusable' );
Adding PHP: https://docs.generatepress.com/article/adding-php/#code-snippets