Bootstrap/site/layouts/partials/docs-sidebar.html

<nav class="bd-links w-100" id="bd-docs-nav" aria-label="Docs navigation">
  {{- $url := split .Permalink "/" -}}
  {{- $page_slug := index $url (sub (len $url) 2) -}}

  <ul class="bd-links-nav list-unstyled mb-0 pb-3 pb-md-2 pe-lg-2">
  {{- range $group := .Site.Data.sidebar -}}
    {{- $link := $group.title -}}
    {{- $link_slug := $link | urlize -}}

    {{- if $group.pages -}}
      {{- $link = index $group.pages 0 -}}
      {{- $link_slug = $link.title | urlize -}}
    {{- end -}}

    {{- $group_slug := $group.title | urlize -}}
    {{- $is_active_group := eq $.Page.Params.group $group_slug -}}

    {{- if $group.pages }}
      <li class="bd-links-group py-2">
        <strong class="bd-links-heading d-flex w-100 align-items-center fw-semibold">
          {{- if $group.icon }}
            <svg class="bi me-2"{{- if $group.icon_color }} style="color: var(--bs-{{ $group.icon_color }});"{{- end }} aria-hidden="true"><use xlink:href="#{{ $group.icon }}"></use></svg>
          {{- end }}
          {{ $group.title }}
        </strong>

        <ul class="list-unstyled fw-normal pb-2 small">
          {{- range $doc := $group.pages -}}
            {{- $doc_slug := $doc.title | urlize -}}
            {{- $is_active := and $is_active_group (eq $page_slug $doc_slug) -}}
            {{- $href := printf "/docs/%s/%s/%s/" $.Site.Params.docs_version $group_slug $doc_slug }}
            <li><a href="{{ $href }}" class="bd-links-link d-inline-block rounded{{ if $is_active }} active{{ end }}"{{ if $is_active }} aria-current="page"{{ end }}>{{ $doc.title }}</a></li>
          {{- end }}
        </ul>
      </li>
    {{- else }}
      <li class="bd-links-span-all mt-1 mb-3 mx-4 border-top"></li>
      <li class="bd-links-span-all">
        <a href="/docs/{{ $.Site.Params.docs_version }}/{{ $group_slug }}/" class="bd-links-link d-inline-block rounded small {{ if $is_active_group }} active{{ end }}"{{ if $is_active_group }} aria-current="page"{{ end }}>
          {{ $group.title }}
        </a>
      </li>
    {{- end }}
  {{- end }}
  </ul>
</nav>