hugo-theme-relearn/layouts/partials/menu.html

<nav id="sidebar" class="{{if $.Site.Params.showVisitedLinks }}showVisitedLinks{{end}}">
  {{ $currentNode := . }}
  {{ $showvisitedlinks := .Site.Params.showVisitedLinks }}
  <div id="header-wrapper">
    <div id="header">
      {{ partial "logo.html" . }}
    </div>
    {{if not .Site.Params.disableSearch}}
        {{ partial "search.html" . }}
    {{end}}
  </div>
  {{if not .Site.Params.disableLandingPageButton }}
    <section id="homelinks">
      <ul>
        <li>
            <a class="padding" href="{{ .Site.Params.landingPageURL | default "/" | relLangURL }}">{{ .Site.Params.landingPageName | default `<i class="fas fa-home"></i> Home` | safeHTML }}</a>
        </li>
      </ul>
    </section>
  {{end}}

  <div class="highlightable">
    <ul class="topics">
      {{if eq .Site.Params.ordersectionsby "title"}}
        {{range .Site.Home.Sections.ByTitle}}
        {{ template "section-tree-nav" dict "sect" . "currentnode" $currentNode "showvisitedlinks" $showvisitedlinks "alwaysopen" false }}
        {{end}}
      {{else}}
        {{range .Site.Home.Sections.ByWeight}}
        {{ template "section-tree-nav" dict "sect" . "currentnode" $currentNode "showvisitedlinks" $showvisitedlinks "alwaysopen" false }}
        {{end}}
      {{end}}
    </ul>

    {{ $disableShortcutsTitle := .Site.Params.DisableShortcutsTitle}}
    {{with .Site.Menus.shortcuts}}
      <section id="shortcuts">
        <h3>{{ if not $disableShortcutsTitle}}{{ T "Shortcuts-Title"}}{{ end }}</h3>
        <ul>
          {{ range sort . "Weight"}}
            <li>
                {{.Pre}}<a class="padding" href="{{.URL | absLangURL }}">{{safeHTML .Name}}</a>{{.Post}}
            </li>
          {{end}}
        </ul>
      </section>
    {{end}}

    {{ if or .Site.IsMultiLingual $showvisitedlinks }}
      <section id="prefooter">
        <hr/>
        <ul>
          {{ if and .Site.IsMultiLingual (not .Site.Params.DisableLanguageSwitchingButton)}}
            <li>
              <a class="padding">
                <i class="fas fa-language fa-fw"></i>
                <div class="select-style">
                  <select id="select-language" onchange="location = this.value;">
                    {{ $siteLanguages := .Site.Languages}}
                    {{ $pageLang := .Page.Lang}}
                    {{ range .Page.AllTranslations }}
                        {{ $translation := .}}
                        {{ range $siteLanguages }}
                            {{ if eq $translation.Lang .Lang }}
                              {{ $selected := false }}
                              {{ if eq $pageLang .Lang}}
                                <option id="{{ $translation.Language }}" value="{{ $translation.Permalink }}" selected>{{ .LanguageName }}</option>
                              {{ else }}
                                <option id="{{ $translation.Language }}" value="{{ $translation.Permalink }}">{{ .LanguageName }}</option>
                              {{ end }}
                            {{ end }}
                        {{ end }}
                    {{ end }}
                  </select>
                  <svg version="1.1" id="Capa_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
                    width="255px" height="255px" viewBox="0 0 255 255" style="enable-background:new 0 0 255 255;" xml:space="preserve">
                    <g>
                      <g id="arrow-drop-down">
                        <polygon points="0,63.75 127.5,191.25 255,63.75 		" />
                      </g>
                    </g>
                  </svg>
                </div>
              </a>
            </li>
          {{end}}

          {{ if $showvisitedlinks}}
            <li><a class="padding" href="#" data-clear-history-toggle=""><i class="fas fa-history fa-fw"></i> {{T "Clear-History"}}</a></li>
          {{ end }}
        </ul>
      </section>
    {{ end }}
    <section id="footer">
      {{ partial "menu-footer.html" . }}
    </section>
  </div>
</nav>

<!-- templates -->
{{ define "section-tree-nav" }}
{{ $showvisitedlinks := .showvisitedlinks }}
{{ $currentNode := .currentnode }}
{{ $currentFileUniqueID := "" }}
{{ $alwaysopen := .alwaysopen }}
{{ with $currentNode.File }}{{ $currentFileUniqueID = .UniqueID }}{{ end }}
  {{with .sect}}
		{{ $hidden := and (or (.Params.hidden) (eq .Title "")) (not $.showhidden) }}
    {{if .IsSection }}
      {{safeHTML .Params.head}}
      {{ $currentAlwaysopen := .Params.alwaysopen | default $alwaysopen }}
      <li data-nav-id="{{.RelPermalink}}" title="{{.Title}}" class="dd-item{{if eq .File.UniqueID $currentFileUniqueID}} active{{end}}{{if .IsAncestor $currentNode }} parent{{end}}{{if $currentAlwaysopen}} alwaysopen{{end}}{{if $hidden}} hidden{{end}}">
        <a href="{{.RelPermalink}}">
          {{ partial "menu-pre.html" . }}{{or .Params.menuTitle .LinkTitle .Title}}{{ partial "menu-post.html" . }}
          {{ if $showvisitedlinks}}<i class="fas fa-check read-icon"></i>{{end}}
        </a>
        <ul>
          {{ $currentNode.Scratch.Set "pages" .Pages }}
          {{ if .Sections}}
            {{ $currentNode.Scratch.Set "pages" (.Pages | union .Sections) }}
          {{end}}
          {{ $pages := ($currentNode.Scratch.Get "pages") }}

          {{if eq .Site.Params.ordersectionsby "title"}}
            {{ range $pages.ByTitle }}
              {{ template "section-tree-nav" dict "sect" . "currentnode" $currentNode "showvisitedlinks" $showvisitedlinks "alwaysopen" true}}
            {{ end }}
          {{else}}
            {{ range $pages.ByWeight }}
            {{ template "section-tree-nav" dict "sect" . "currentnode" $currentNode "showvisitedlinks" $showvisitedlinks "alwaysopen" true}}
            {{ end }}
          {{end}}
        </ul>
      </li>
    {{else}}
      <li data-nav-id="{{.RelPermalink}}" title="{{.Title}}" class="dd-item{{if eq .File.UniqueID $currentFileUniqueID}} active{{end}}">
        <a href="{{ .RelPermalink}}">
          {{ partial "menu-pre.html" . }}{{or .Params.menuTitle .LinkTitle .Title}}{{ partial "menu-post.html" . }}
          {{ if $showvisitedlinks}}<i class="fas fa-check read-icon"></i>{{end}}
        </a>
      </li>
    {{end}}
  {{ end }}
{{ end }}