Linked Products feature guideline:

Products can be Related to each other in three ways: Up-Sells, Cross-Sells or by having the same tags or categories. 

Related Products 

Related Products is a section of our shop which pulls products from your store that share the same tags or categories as the current product automatically.

These products cannot be specified in the admin, but can be influenced by grouping similar products in the same category or by using the same tags.

• Related products (automatic) also show on the product page.
• Related products always prioritize the Parent Category

To add an up-sell or cross-sell to a product:

1. Go to WooCommerce > Products and select the product on which you’d like to show an up-sell or cross-sell
2. Scroll down to the Product Data panel
3. Select the Linked Products tab in the left menu
4. Add the product you wish to link to by searching for it
5. Update

Linked products always work and look best in groups of 3. 

Up-Sells

Up-sells are products that you recommend instead of the currently viewed product.

They are typically products that are more profitable or better quality or more expensive. Depending on your theme template, these products display on the single product page underneath the product’s description.

• Up-sells (user defined) show on the product page

Cross-Sells

Cross-sells are products that you promote in the cart, based on the current product.

They are typically complementary items. For example, if you are selling a laptop, cross-sells might be a protective case or stickers or a special adapter. Or if you’re selling a ninja t-shirt, they could be a ninja hoodie and ninja socks.

Depending on your theme template, they display on the cart page underneath the cart products table with a thumbnail image.

• Cross-sells (user defined) show on the cart page.