经过一些测试，我发现最好的方法是使用助行器。

对于本例，我们假设这是调用菜单的代码

wp_nav_menu([
    \'container\'        => false,
    \'theme_location\'   => \'right-side-top-menu\',
    \'walker\'           => new Menu_Middle_Logo()
]);

现在对于我们的walker来说，没有一种简单的方法来确定哪个父菜单项是中间的菜单项，但这段代码应该能够处理您的每个顶级菜单项场景。

class Menu_Middle_Logo extends Walker_Nav_Menu {
    function end_el (&$output, $item, $depth = 0, $args = [], $id = 0) {
        parent::end_el($output, $item, $depth, $args, $id);
        
        // the menu slug
        $theme_location = \'right-side-top-menu\';
        
        // check for top level depth and if correct menu
        if ($depth === 0 && isset($args->menu) && isset($args->menu->slug) && $args->menu->slug === $theme_location) {
            // get current menu items
            $menu_items = wp_get_nav_menu_items($theme_location);
            
            // will indicate how many top level menu items we have
            $parent_menu_items = [];
            
            // get top level menu items
            foreach ($menu_items as $menu_item) {
                if ($menu_item->menu_item_parent == 0) $parent_menu_items[] = $menu_item;
            }
            
            // get total menu items halved
            $half_menu_items = floor(count($parent_menu_items) / 2);
            
            // the menu item we want to add the logo to
            // before or after, depends if menu items are odd or even
            if (is_float($half_menu_items)) {
                // if you have odd menu items lets say three this will add after the first
                // [1] [custom html] [2] [3]
                // if you want it to add after the second remove the - 1, this will result in
                // [1] [2] [custom html] [3]
                $middle_item = $parent_menu_items[$half_menu_items - 1];
            } elseif (is_int($half_menu_items)) {
                // this handles even menu items
                $middle_item = $parent_menu_items[$half_menu_items - 1];
            }
            
            // if current menu item is middle item, add our custom html
            if (isset($middle_item) && $middle_item->ID === $item->ID) {
                $output .= \'<li class="my-logo">\';
                
                ob_start();
                the_custom_logo();
                // this is for testing because the_custom_logo()
                // is not available in my theme
                // echo 1234; 
                $output .= ob_get_clean();
                
                $output .= \'</li>\';
            }
        }
    }
}

将此walker代码复制到functions.php 它应该会起作用
别忘了在中添加walker属性wp_nav_menu args。