As mentioned above, there are some purchases that can be made through the PSN storefront, and those ones can be added to the cart like your screenshot above. Other purchases which can only be done in game unfortunately cannot be added to the cart like in the screenshot above, due to the nature of the purchases.
Some other free-to-play games like Warframe have their premium currency purchases made through the storefront. I haven’t personally seen if there are any other purchases in-game which are not available on the PS4 storefront, but I would assume that they would have a similar issue to what you are seeing above.