Is it possible to separate all submenu items?

Question

I'm using FoundationPress as a starter theme and I'm trying to separate the submenu. My theme basically generates menus like this:

<ul>
    <li class=" first-level has-dropdown">
        <ul class="submenu>
            <li class="second-level"><a>link</a></li>
            <li class="second-level"><a>link</a></li>
            <li class="second-level"><a>link</a></li>
        </ul>
    </li>
    <li class="first-level"><a>link</a></li>
    <li class="first-level"><a>link</a></li>
    <li class="first-level"><a>link</a></li>
</ul>

What I'm trying to get is:

<ul>
    <li class=" first-level has-dropdown"></li>
    <li class="first-level"><a>link</a></li>
    <li class="first-level"><a>link</a></li>
    <li class="first-level"><a>link</a></li>
</ul>

<div class="submenu>
    <li class="sub-menus-of-all-levels"><a>link</a></li>
    <li class="sub-menus-of-all-levels"><a>link</a></li>
    <li class="sub-menus-of-all-levels"><a>link</a></li>
</div>

I've had trouble with custom Walkers. How can I solve this?

Answer 1

Use wp_get_nav_menu_items() and print a menu item from the data of the returned object if it doesn't got menu_item_parent set.