WordPress filter to replace top level menu items with buttons

navigation.php

<?php

function edit_menu_item($item_output, $item) {
	if ( in_array('menu-item-has-children', $item->classes) ) { 
			return '<button type="button" aria-expanded="false" id="' . $item->title . '-' . $item->ID . '">'.$item->title.'</button>';
	}
	return $item_output;
}
add_filter('walker_nav_menu_start_el','edit_menu_item', 10, 2);