<div id="wrap">

  <!-- section -->
  <div class="section">
    <div class="center">

      <div id="menu">
        <div id="menu-list">
          <div class="menu-item">
            <span>menu item</span>
          </div>
        </div>
      </div>

      <button id="add">ADD MENU</button>

    </div>
  </div>
  <!--/section -->

</div>

html,
body {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
  font-size: 16px;
  line-height: 1.4;
  color: #555;
  background: #fff;
}

* {
  box-sizing: border-box;
}

#wrap {
  position: relative;
}

.section {
  padding: 40px;
}

.center {
  width: 100%;
  max-width: 980px;
  margin: auto;
}

#menu {
  width: 200px;
  height: 300px;
  box-shadow: 0 0 0 1px #000;
  margin-bottom: 20px;
  
  &-list {
    padding: 3px 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
  }
}

.menu-item {
  box-shadow: inset 0 0 0 1px #aaa;
  margin: 3px 6px;
  flex: 1 0 auto;
  background: fade(#00baff, 10%);
  display: flex;
  align-items: center;
  padding: 0 6px;
  font-size: 11px;
}

$(function () {
  $('#add').click(function() {
    $('.menu-item').last().clone().appendTo('#menu-list');
  });
});