zdoc/layouts/partials/main/sections/single-menu.html

<div class="menu">
  <h6 class="menu__label">
    {{ if .IsHome }}
      {{ .Site.Title }}
    {{ else }}
      {{ .Type }}
    {{ end }}
  </h6>
  <ul>
    {{ $currentURL := .Permalink }}
    {{ range (.Site.GetPage "section" .Type).Pages }}
      {{ $sectionName1 := index (last 1 (split (delimit (split .Permalink "/") "," "") ",")) 0 }}
      {{ $sectionName2 := index (last 2 (split (delimit (split $currentURL "/") "," "") ",")) 0 }}
      {{ if .Params.Collapsible }}
        <span class="menu__title--collapse {{ if and (in $currentURL .Permalink) (eq $sectionName1 $sectionName2) }}active{{ end }}">
          {{ .Title }}
          <span class="menu__title--icon {{ if and (in $currentURL .Permalink) (eq $sectionName1 $sectionName2) }}down{{ else }}right{{ end }}">
            {{ partial "svgs/arrow-right.svg" (dict "width" 22 "height" 22) }}
          </span>
        </span>
        <ul class="menu__list {{ if and (in $currentURL .Permalink) (eq $sectionName1 $sectionName2) }}active{{ end }}">
          {{ range .Pages.ByWeight }}
            {{ $lastUrlElement1 := index (last 1 (split (delimit (split .Permalink "/") "," "") ",")) 0 }}
            {{ $lastUrlElement2 := index (last 1 (split (delimit (split $currentURL "/") "," "") ",")) 0 }}
            <li>
              <a href="{{ .Permalink }}" class="menu__title {{ if and (eq $lastUrlElement1 $lastUrlElement2) (eq $sectionName1 $sectionName2) }}active{{ end }}">{{ .Title }}</a>
            </li>
          {{ end }}
        </ul>
      {{ else }}
        {{ $lastUrlElement1 := index (last 1 (split (delimit (split .Permalink "/") "," "") ",")) 0 }}
        {{ $lastUrlElement2 := index (last 1 (split (delimit (split $currentURL "/") "," "") ",")) 0 }}
        <li>
          <a href="{{ .Permalink }}" class="menu__title {{ if in $lastUrlElement1 $lastUrlElement2 }}active{{ end }}">{{ .Title }}</a>
        </li>
      {{ end }}
    {{ end }}
  </ul>
</div>