They are intended to cross-sell products on the cart review page the same way the Extras settings do: show a product strip on the cart, open a pop-up suggesting products, and repeat that pop-up on every visit. In the current version, however, the cart page only implements this behaviour for Extras - a codebase-wide search found no place that reads the Products versions of these keys outside the settings screen itself - so these three rows have no visible effect for products right now. Use the Extras module's equivalents if you need cart cross-selling.