Hello,
WooCommerce does not have the option to set the related products from Dashboard, it takes them automatically by category or tag. Please read more in the article from my previous message.
You have set Up-Sells and Cross-Sells products – https://prnt.sc/CJRdMpmO9jRn , so go to Single Product Builder > add elements into the content area – https://prnt.sc/2Fz7vVeKt-cn
Regards