Reply To: Customize Related Products on Product Page

What works well for me is to turn related products off in theme settings and use Woocommerce Upsells to add the relevant products you want to promote on each product page as related products.

Its laborious if you have a large site but worth the work if you have important products you want to cross sell / up sell. I get a lot of additional orders by individually selecting what products I want to promote as related products for each product page.