Hi kkriss,
Do you mean the SKU?
In this case, you’l need to add a custom column to your wishlist template; follow this steps:
1. Copy wishlist-view.php template from wp-content/plugins/yith-woocommerce-wishlist/templates to your theme root
2. Edit this new file as follow
a. Increase non-optional column count from 2 to 3 at line 53
<?php $column_count = 3; ?>
b. Add a column to thead (i.e. after product name, at line 80)
<th class="product-sku">
<span class="nobr"><?php _e( 'Cod.', 'yith-woocommerce-wishlist' ) ?></span>
</th>
c. Add column content to tbody (if you want to insert this after product name, you will add td at around line 162)
<td class="product-sku">
<?php echo ( ! empty( $product->sku ) ) ? $product->sku : __( 'N/A', 'yith-woocommerce-wishlist' ) ?>
</td>
Here there are some screen of the test on my local installation
https://screencast.com/t/w0w9mBCqOwD
https://screencast.com/t/WjXKpQ0E
Let me know if this helps
Have a nice day ??