if ( ! function_exists( ‘woocommerce_template_loop_product_title’ ) )
{
/** * Show the product title in the product loop. By default this is an H2. */
function woocommerce_template_loop_product_title()
{
echo ‘<h3 class=”woocommerce-loop-product__title”>’ . get_the_title() . ‘</h3>’;
}
}
Tham khảo: https://wordpress.org/support/topic/change-loop-title-from-h2-to-h4/