原来某个网店里，就有这个要求。现在要做同样的功能，找了半天，不知从哪里下手，给忘了怎么弄了！
现在记录一下步骤：

1, includes/index_filters/default_filter.php
大概72行的位置，把那段SQL注译了，写：

$listing_sql = "select " . $select_column_list . " p.products_id, p.products_type, p.master_categories_id, p.manufacturers_id, p.products_price, p.products_tax_class_id, pd.products_description, IF(s.status = 1, s.specials_new_products_price, NULL) as specials_new_products_price, IF(s.status =1, s.specials_new_products_price, p.products_price) as final_price, p.products_sort_order, p.product_is_call, p.product_is_always_free_shipping, p.products_qty_box_status
       from " . TABLE_PRODUCTS_DESCRIPTION . " pd, " .
       TABLE_PRODUCTS . " p left join " . TABLE_MANUFACTURERS . " m on p.manufacturers_id = m.manufacturers_id, " .
       TABLE_PRODUCTS_TO_CATEGORIES . " p2c left join " . TABLE_SPECIALS . " s on p2c.products_id = s.products_id
       where p.products_status = 1
         and p.products_id = p2c.products_id
         and pd.products_id = p2c.products_id
         and pd.language_id = '" . (int)$_SESSION['languages_id'] . "'
         and FIND_IN_SET(p2c.categories_id, F_GET_SUB_CATEGORIES(  " . (int)$current_category_id ."))".
         $alpha_sort;


        
2，新建一个存储过程和一个函数到MYSQL里：

--please replace all 'zen' to your database prefix.

DELIMITER //

CREATE PROCEDURE P_GET_SUB_CATEGORIES(IN IN_CATID INT,OUT OUT_IDS VARCHAR(1000))
BEGIN
    DECLARE V_STOP BOOLEAN DEFAULT FALSE;
    DECLARE V_IDS VARCHAR(1000);
    DECLARE V_ID INT;
    DECLARE V_SUB_IDS VARCHAR(1000);
    DECLARE CUR1 CURSOR FOR SELECT categories_id FROM zen_categories WHERE parent_id = IN_CATID;
    DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET V_STOP = TRUE;
   
    OPEN CUR1;

    SET @@max_sp_recursion_depth = 10;

    LAB1:WHILE NOT V_STOP DO
        FETCH CUR1 INTO V_ID;
        IF V_STOP THEN
            LEAVE LAB1;
        END IF;

        CALL P_GET_SUB_CATEGORIES(V_ID,V_SUB_IDS);
        SET V_IDS = CONCAT_WS(',',V_IDS,V_ID,V_SUB_IDS);
    END WHILE LAB1;
    SET OUT_IDS = V_IDS;
END//

CREATE FUNCTION F_GET_SUB_CATEGORIES(IN_CATID INT) RETURNS VARCHAR(3000)
BEGIN
    DECLARE V_CATS VARCHAR(1000);
    CALL P_GET_SUB_CATEGORIES(IN_CATID,V_CATS);
    RETURN CONCAT_WS(',',IN_CATID,V_CATS);
END//

DELIMITER ;



3，includes/modules/pages/index/main_template_vars.php :
大概62行，改成:
if( $category_depth == 'nested______' ){
目的就是不让 $category_depth 不匹配 nested

然后修改：
elseif( $category_depth == 'products' || zen_check_url_get_terms( ) ){
为：
}elseif($category_depth == 'nested' || $category_depth == 'products' || zen_check_url_get_terms( ) ){

OK。