Until now, the complementary products (cross-selling) widget only showed on the product page and in the cart. From now on you can also show it at checkout, right before the customer pays — one more chance to add sales at the last step of the purchase.
To turn it on: go to your Complementary products widget, General tab, and enable "Show at checkout." If you create a new widget, this option already comes turned on by default. If you already had one set up, you need to turn it on yourself. 🛍️