再次感谢jdm2112的帮助。更新了一些语法错误，并使用了您建议的相同结构，效果很好！

// Add notification bubble to custom post type menu nav 
add_action( \'admin_menu\', \'add_cpt_menu_bubble\' );
function add_cpt_menu_bubble() {
    global $menu;
    $count_posts = tms_count_pending_posts();
    if ( $count_posts > 3 ) {
        foreach ( $menu as $key => $value ) {
            if ( $menu[$key][2] == \'edit.php?post_type=custom_post_type_name\' ) {
                $menu[$key][0] .= \' <span class="update-plugins count-2"><span class="update-count">\' . $count_posts . \'</span></span>\';
                return;
            }
        }
    }
}
function tms_count_pending_posts() {
    if ( false === ( $num_posts = get_transient( \'tms_pending_posts_key\' ) ) ) {
        $args = array(
            \'order\'    => \'DESC\',
            \'posts_per_page\' => \'-1\',
            \'post_type\' => \'custom_post_type_name\',
            \'custom_tax\' => \'pending-review\'
        );
        $posttype_query = new WP_Query( $args );
        ($posttype_query->post_count) ? $num_posts = $posttype_query->post_count : $num_posts = 0;
        set_transient( \'tms_pending_posts_key\', $num_posts, 30 ); 
    } 
    return $num_posts;
}

使用您的原始代码，我将查询/计数/缓存代码拉到一个单独的函数中。我还没有机会测试这些，所以如果您遇到任何错误，我深表歉意。如果你这样做了，请在这里发布，我会在测试时更新。

简单地说，想法是首先根据每个值唯一的键（名称）检查有效的瞬态，如果不存在值，则重新创建并存储它。无论哪种方式，调用函数都应返回posttype 帖子，最长4小时。

我随机选择了4个小时，但这是一个容易编辑的参数。只要想出一些东西来代替“你的临时钥匙”，你就可以很好地使用了。

add_action( \'admin_menu\', \'add_cpt_menu_bubble\' );
function add_cpt_menu_bubble() {
    global $menu;

    // Retrieve cached value or count current number of posttype posts.
$count_posts = wpse_count_of_posttype_posts

    // only display the number of pending posts over a certain amount
    if ( $count_posts > 5 ) {
        foreach ( $menu as $key => $value ) {
            if ( $menu[$key][2] == \'edit.php?post_type=custom_post_type_name\' ) {
                $menu[$key][0] .= \' <span class="update-plugins count-2"><span class="update-count">\' . $count_posts . \'</span></span>\';
                return;
            }
        }
    }

}

function wpse_count_of_postype_posts() {

    // First try to get a cached value
    if ( false === ( $num_posts = get_transient( \'your-transient-key\' ) ) ) {
        // this code runs when there is no valid transient set

        // Your original query args
        $args = array(
            \'order\'    => \'DESC\',
            \'posts_per_page\' => \'-1\',
            \'post_type\' => \'custom_post_type_name\',
            \'custom_tax_name\' => \'pending-review\'
        );

        // Instantiate WP_Query instead
        $posttype_query = new WP_Query( $args );

        // One of the properties of the class is a count of the posts. No need to loop and increment a counter
        // https://codex.wordpress.org/Class_Reference/WP_Query#Properties
        $num_posts = $posttype_query->post_count;

        // Store the count in your transient; build it now for the future https://www.youtube.com/watch?v=XjYLvpwDNOY
        set_transient( \'your-transient-key\', $num_posts, 4 * HOUR_IN_SECONDS );

        return $num_posts;
    }
}