custom-nav-elements.twig

{% set navElements = { 1: 'section', 2: 'article' } %}

{% nav entry in entries %}

    {# fetch the HTML element matching the entry level #}
    <{{ navElements[entry.level]|default('div') }}>

        {{ entry.content }}
        
        {% ifchildren %}
            {% children %}
        {% endifchildren %}

    {# close it off with the same element #}        
    </{{ navElements[entry.level]|default('div') }}>
    
{% endnav %}