Merging Two menus in the backend into one menu

<div class="menu-wrapper">
   <div class="menu1">
     <?php
            wp_nav_menu( array(
                'theme_location'  => 'menu-1',
                'menu_id'         => 'top-menu',
            ) );
        ?>
   </div>
   <div class="menu2">
     <?php
            wp_nav_menu( array(
                'theme_location'  => 'menu-2',
                'menu_id'         => 'main-menu',
            ) );
        ?>
   </div>
</div>