向下拉菜单中添加自定义链接到magento 2菜单

Question

我正在尝试将自定义菜单链接添加到我的magento网站。我只设法添加了顶层，但不知道如何添加下拉菜单（嵌套的子项）。

    public function beforeGetHtml(
        \Magento\Theme\Block\Html\Topmenu $subject,

        $outermostClass = '',
        $childrenWrapClass = '',
        $limit = 0
    ) {
        // Add custom page in menu


            $node = $this->nodeFactory->create(
                [
                    'data' => [
                        'name' => __('Custom menu'),
                        'id' => 'customMenu',
                        'url' => $this->_urlBuilder->getUrl(null, ['_direct' =>'custommenu']),
                        'has_active' => false,
                        'is_active' => false
                    ],
                    'idField' => 'id',
                    'tree' => $subject->getMenu()->getTree()
                ]
            );
            $subject->getMenu()->addChild($node);
    }