netbox-community-netbox/netbox/utilities/templates/navigation/nav_items.html

<div id="sidenav-accordion" class="accordion accordion-flush nav-item">
  {% for menu in nav_items %}
  <div class="accordion-item">
    <a
      href="#"
      role="button"
      aria-expanded="true"
      data-bs-toggle="collapse"
      data-bs-target="#{{ menu.label|lower }}"
      class="d-flex justify-content-between align-items-center accordion-button nav-link collapsed">
        <span class="fw-bold sidebar-nav-link">
          {{ menu.label }}
        </span>
      </a>
    <div id="{{ menu.label|lower }}" class="accordion-collapse collapse" data-bs-parent="#sidenav-accordion">
      <div class="multi-level accordion-body px-0">
        {% for group in menu.groups %}
        <div class="flex-column nav px-2">
          {% if menu.groups|length > 1 %}
          <h6 class="accordion-item-title">{{ group.label }}</h6>
          {% endif %} {% for item in group.items %}
          <div class="nav-item">
            <a class="nav-link" href="{% url item.url %}">{{ item.label }}</a>
          </div>
          {% endfor %}
        </div>
        {% if forloop.counter != menu.groups|length %}
        <hr class="dropdown-divider my-2" />
        {% endif %} {% endfor %}
      </div>
    </div>
  </div>
  {% endfor %}
</div>