A lot of stores will never need to use this feature, as we'll automatically calculate good recommendations for your store based on purchase history, and on your Shopify Collections).
But there are a few occasions where you might want to override the automatic suggestions with relationships of your own.
Suppose you've got lots of sales and lots of products. When you introduce a new product, it doesn't have a purchase history yet so we don't know what to recommend it with. Over time, as the product gets sales, Better Recommendations learns what products it relates to, but you might want to kick-start this with a manual recommendation.
You're introducing a belt that matches a particular pair of shoes, so you want to suggest the belt for anyone purchasing the shoes, but they aren't in the same Collection.
You might want to use manual recommendations to bootstrap the suggestions that get made for a new store, where there's no order history (or only a handful of orders) that we can use to automatically generate the recommendations.
You're setting up a camera store on Shopify. You might have a collection of SLRs, and another collection of flashes. You want people who buy a camera to consider buying a flash alongside it, so you can manually recommend a flash that goes well with each of the different models of SLR.
You can use manual recommendations to push a product that you'd like to see performing better.
By setting up manual recommendation relationship with a more popular product, it will be shown to more of your customers.
In most cases the automatic recommendations should "catch up" with the manual recommendations, simply because your customers are more likely to buy the products together.
When you set up a manual recommendation, we treat it as if lots of the people who buy product on the left also go on buy the products on the right.
If someone is looking at the page for the product on the left, we'll show the products on the right as recommendations.
On the cart page, the suggestions we show depend on all the items in the basket, but if the product on the left is in the basket we're more likely to show the manual recommendations you've set up amongst the cart page recommendations.