Is it possible to show a pop-up cart after adding products to the cart with Frequently Bought Together?
In order to add products to the shopping cart, the app uses the Shopify Ajax API, which is indeed the official way to do it.
However, some themes integrate pop-up carts and given the large variety of themes in Shopify, there isn't any standard mechanism to handle these pop-up carts in every theme yet.
With regard to displaying the shopping cart contents, Frequently Bought Together redirects to the cart page automatically after clicking on the add-to-cart button but it is not possible to trigger the pop-up carts at the moment.
We will continue improving the support for pop-up carts and other features in future versions of the app.