Thanks so much for the quick reply. Where exactly do i paste it? I have made an attempt below, but not sure if this is the right placement.
<h3
class="card__heading"
{% if card_product.featured_media == null and settings.card_style == 'standard' %}
id="title-{{ section_id }}-{{ card_product.id }}"
card_product.custom.product_subtitle
{% endif %}