On the products page I have 'related products' visible.

On the products page I have 'related products' visible. Turned on in the 'Store Settings'.
However I need to to show *global* related products using category. I only have two stores but both need to be shown in 'related products'.
If I need to create it in mp_product.php in my child theme please advise the php or shortcode to make current item and related items visible.