bootstrap4.css
.breadcrumb {
  display: -ms-flexbox;
  display: flex;
  -ms-flex-wrap: wrap;
  flex-wrap: wrap;
  padding: 0.75rem 1rem;
  margin-bottom: 1rem;
  list-style: none;
  background-color: #e9ecef;
  border-radius: 0.25rem;
}
bootstrap4.css
.breadcrumb-item + .breadcrumb-item {
  padding-left: 0.5rem;
}
bootstrap4.css
.breadcrumb-item + .breadcrumb-item::before {
  display: inline-block;
  padding-right: 0.5rem;
  color: #6c757d;
  content: "/";
}
bootstrap4.css
.breadcrumb-item + .breadcrumb-item:hover::before {
  text-decoration: underline;
}
bootstrap4.css
.breadcrumb-item + .breadcrumb-item:hover::before {
  text-decoration: none;
}
bootstrap4.css
.breadcrumb-item.active {
  color: #6c757d;
}
■ナビゲーション水平方向、均等:nav:コンポーネント:コンポーネント:パンくずリスト TODO独自CSS直す必要あり

  <nav aria-label="breadcrumb" role="navigation">
    <ol class="breadcrumb">
      <li class="breadcrumb-item"><a href="#">ホーム</a></li>
      <li class="breadcrumb-item"><a href="#">ライブラリー</a></li>
      <li class="breadcrumb-item active" aria-current="page">データ</li>
    </ol>
  </nav>