layouts/shortcodes/marginpar.html

{{- $marginparID := print "marginpar-" .Ordinal }}
<input id="{{ $marginparID }}" class="marginpar-ctrl" type="checkbox" aria-label="{{ i18n "marginpar" }}" aria-controls="the-{{ $marginparID }}" hidden>
<label for="{{ $marginparID }}" tabindex="0" role="checkbox" aria-label="{{ i18n "marginpar" }}" aria-controls="the-{{ $marginparID }}" aria-expanded="undefined"></label>
<span id="the-{{ $marginparID }}" class="marginpar" role="note">{{ .Inner | markdownify }}</span>