Bulma 0.6 implementation of the megamenu extension https://github.com/hunzaboy/bulma-megamenu

megamenu.bulma.html

<nav class="navbar">

  <div class="navbar-brand">
    <div class="navbar-burger burger" data-target="navMenubd-example">
      <span></span>
      <span></span>
      <span></span>
    </div>
  </div>

  <div class="navbar-menu">
    <div class="navbar-start">
      
      <!-- simple dropdown menu -->
      <div class="navbar-item has-dropdown is-hoverable">
        <a href="#" class="navbar-link">Docs</a>
        <div class="navbar-dropdown">
          <a href="#" class="navbar-item">Overview</a>
          <a href="#" class="navbar-item">Modifiers</a>
          <a href="#" class="navbar-item">Columns</a>
          <a href="#" class="navbar-item">Layout</a>
          <a href="#" class="navbar-item">Form</a>
          <a href="#" class="navbar-item">Elements</a>
          <a href="#" class="navbar-item">Components</a>

          <hr class="navbar-divider">

          <div class="navbar-item">
            <div>
              <p class="is-size-6-desktop">
                <strong class="has-text-info">0.5.1</strong>
              </p>
            </div>
          </div>
        </div>
      </div>

      <!-- mega dropdown menu -->
      <div class="navbar-item has-dropdown is-hoverable is-mega">
        <a class="navbar-link">
          Blog
        </a>
        <div class="navbar-dropdown">
          <div class="container is-fluid">
            <div class="columns">
              <div class="column">
                <h1 class="title is-size-6 is-mega-menu-title">Sub Menu Title</h1>
                <a href="#" class="navbar-item">
                  <div class="navbar-content">
                    <p>
                      <small class="has-text-info">03 Aug 2017</small>
                    </p>
                    <p>New feature: list of tags</p>
                  </div>
                </a>
                <a href="#" class="navbar-item">
                  <div class="navbar-content">
                    <p>
                      <small class="has-text-info">03 Aug 2017</small>
                    </p>
                    <p>New feature: list of tags</p>
                  </div>
                </a>
                <a href="#" class="navbar-item">
                  <div class="navbar-content">
                    <p>
                      <small class="has-text-info">03 Aug 2017</small>
                    </p>
                    <p>New feature: list of tags</p>
                  </div>
                </a>
              </div>
              <div class="column">
                <h1 class="title is-size-6 is-mega-menu-title">Sub Menu Title</h1>
                <a href="#" class="navbar-item">
                  <div class="navbar-content">
                    <p>
                      <small class="has-text-info">03 Aug 2017</small>
                    </p>
                    <p>New feature: list of tags</p>
                  </div>
                </a>
                <a href="#" class="navbar-item">
                  Overview
                </a>
                <a href="#" class="navbar-item">
                  Modifiers
                </a>
                <a href="#" class="navbar-item">
                  Columns
                </a>
              </div>
              <div class="column">
                <h1 class="title is-6 is-mega-menu-title">Sub Menu Title</h1>
                <a href="#" class="navbar-item">
                  <div class="navbar-content">
                    <p>
                      <small class="has-text-info">03 Aug 2017</small>
                    </p>
                    <p>New feature: list of tags</p>
                  </div>
                </a>
                <a href="#" class="navbar-item">
                  <div class="navbar-content">
                    <p>
                      <small class="has-text-info">03 Aug 2017</small>
                    </p>
                    <p>New feature: list of tags</p>
                  </div>
                </a>
                <a href="#" class="navbar-item">
                  <div class="navbar-content">
                    <p>
                      <small class="has-text-info">03 Aug 2017</small>
                    </p>
                    <p>New feature: list of tags</p>
                  </div>
                </a>
              </div>
              <div class="column">
                <h1 class="title is-6 is-mega-menu-title">Sub Menu Title</h1>
                <a href="#" class="navbar-item">Overview</a>
                <a href="#" class="navbar-item">Modifiers</a>
                <a href="#" class="navbar-item">Columns</a>
                <a href="#" class="navbar-item">Layout</a>
              </div>
            </div>
          </div>

          <hr class="navbar-divider">

          <div class="navbar-item">
            <div class="navbar-content">
              <div class="level is-mobile">
                <div class="level-left">
                  <div class="level-item">
                    <strong>Stay up to date!</strong>
                  </div>
                </div>
                <div class="level-right">
                  <div class="level-item">
                    <a href="#" class="button is-small">
                      <i class="fa fa-sm fa-rss"></i>
                      Subscribe
                    </a>
                  </div>
                </div>
              </div>
            </div>
          </div>
        </div>
      </div>

      <!-- simple dropdown menu w/ levels -->
      <div class="navbar-item has-dropdown is-hoverable">
        <div class="navbar-link">
          More
        </div>
        <div id="moreDropdown" class="navbar-dropdown ">
          <a href="#" class="navbar-item">
            <div class="level is-mobile">
              <div class="level-left">
                <div class="level-item">
                  <p>
                    <strong>Extensions</strong>
                    <br>
                    <small>Side projects to enhance Bulma</small>
                  </p>
                </div>
              </div>
              <div class="level-right">
                <div class="level-item">
                  <span class="icon has-text-info">
                    <i class="fa fa-plug"></i>
                  </span>
                </div>
              </div>
            </div>
          </a>
        </div>
      </div>
    </div>
  </div>
</nav>

megamenu.bulma.js

document.addEventListener('DOMContentLoaded', function () {

  // Get all "navbar-burger" elements
  var $navbarBurgers = Array.prototype.slice.call(document.querySelectorAll('.navbar-burger'), 0);

  // Check if there are any nav burgers
  if ($navbarBurgers.length > 0) {

    // Add a click event on each of them
    $navbarBurgers.forEach(function ($el) {
      $el.addEventListener('click', function () {

        // Get the target from the "data-target" attribute
        var target = $el.dataset.target;
        var $target = document.getElementById(target);

        // Toggle the class on both the "navbar-burger" and the "navbar-menu"
        $el.classList.toggle('is-active');
        $target.classList.toggle('is-active');

      });
    });
  }

});

megamenu.bulma.scss

/**
 * Bulma extension to make Mega Menus
 *
 * @link https://github.com/hunzaboy/bulma-megamenu
 */

.navbar-item.is-mega {
  position: static;

  .is-mega-menu-title {
    margin-bottom: 0;
    padding: .375rem 1rem;
  }
}