Oxygen’s Categories List element isn’t currently able to display WooCommerce parent categories only. However, there is a simple workaround using Oxygen’s Code Block element. To use the workaround, add a Code Block to your design and set the width of the Code Block to 100% via Advanced > Size & Spacing.

Next, add the following PHP to the Code Block:

<?php
$terms = get_terms(['taxonomy' => 'product_cat', 'hide_empty' => false, 'parent' => 0]);

if ($terms)
{ ?>

<div class="oxy-woo-product-categories oxy-woo-element">
   <div class="woocommerce columns-4">
      <ul class="products columns-4">
  
  <?php
    foreach ($terms as $term)
    {
        // GET IMAGE
        // get the thumbnail id
        $thumbnail_id = get_woocommerce_term_meta($term->term_id, 'thumbnail_id', true);

        // get the image URL
        $image = wp_get_attachment_url($thumbnail_id);
        $srcset = wp_get_attachment_image_srcset($thumbnail_id, array(
            300,
            300
        ));

        if (empty($image))
        {
            $image = '/wp-content/uploads/woocommerce-placeholder-300x300.png';
        }

        // GET NAME
        $cat_name = $term->name;

        // GET URL
        $cat_url = get_term_link($term->term_id, 'product_cat');

?>

         <li class="product-category product first">
            <a href="<?php echo $cat_url; ?>">
               <img src="<?php echo $image; ?>" srcset="<?php echo esc_attr($srcset); ?>" alt="<?php echo $cat_name; ?>" width="300" height="300">		
               <h2 class="woocommerce-loop-category__title">
                  <?php echo $cat_name; ?>	
               </h2>
            </a>
         </li>

<?php
    }

?>
  
      </ul>
   </div>
</div>

<?php
}

?>

That should be all you need to do to see your parent categories! If you wish to hide empty categories, then you can set “hide_empty” to “true” on the second line.