skouter/grav-admin/user/themes/quark/templates/partials/layout.html.twig

{% set item_col = show_sidebar ? 'col-9 col-md-12' : 'col-12' %}
{% set sidebar_col = show_sidebar ? 'col-3 col-md-12' : 'col-12' %}

<div class="columns">
    <div id="item" class="column {{ item_col }} extra-spacing">
        {% block item %}{% endblock %}
    </div>
    {% if show_sidebar %}
    <div id="sidebar" class="column {{ sidebar_col }}">
        {% block sidebar %}{% endblock %}
    </div>
    {% endif %}
</div>