vendure/docs/layouts/partials/docs/menu-filetree.html

<!-- Put configured sections list to .Scratch -->
{{ template "book-get-root-section" . }}

{{- range .Scratch.Get "BookSections" -}}
  {{ template "book-section" (dict "Section" . "CurrentPage" $.Permalink) }}
{{- end -}}

{{ define "book-section" }} <!-- Single section of menu (recursive) -->
<ul {{ if .Expanded }}class="expanded"{{ end }}>
    {{ $list := .Section.Sections }}
    {{ $list = $list | append .Section.Pages }}
    {{ range ($list.ByParam "Title").ByParam "Weight" }}
        {{ if eq .Kind "section" }}
            <li class="section">
                {{ $expanded := in $.CurrentPage .Permalink }}
                <div class="section-link">
                <img src="{{ "svg/clr-icon-angle.svg" | relURL }}" class="section-icon {{ if $expanded}}expanded{{ end }}" />
                {{ template "book-page-link" (dict "Page" . "CurrentPage" $.CurrentPage) }}
                </div>
                {{ template "book-section" (dict "Section" . "CurrentPage" $.CurrentPage "Expanded" $expanded) }}
            </li>
        {{ else }}
            <li>
                {{ template "book-page-link" (dict "Page" . "CurrentPage" $.CurrentPage) }}
            </li>
        {{ end }}
    {{ end }}
  </ul>
{{ end }}

{{ define "book-page-link" }}
{{- with .Page -}}
<a href="{{ .RelPermalink }}" {{- if eq $.CurrentPage .Permalink }} class="active"{{ end }}>
  {{- template "title" . -}}
</a>
{{- end -}}
{{ end }}

{{ define "book-get-root-section" }}
<!-- Complex logic to guess page title without .Title specified -->
  {{ $bookSection := default "docs" .Site.Params.BookSection  }}
  {{ if eq $bookSection "*" }}
    {{ .Scratch.Set "BookSections" .Site.Sections }}
  {{ else }}
    {{ $bookSections := where .Site.Sections "Section" $bookSection }}
    {{ .Scratch.Set "BookSections" $bookSections }}
  {{ end }}
{{ end }}