Hi.
The whole industry doesn't do that, you need to create many products with different sets of in-game products and offer them to the user.
I agree, when creating a product in the developer cabinet you can activate the checkbox “purchase multiple items in one transaction”
I as a person with experience recommend not to use this in any case.
Google bot very carefully checks such purchases and often rejects, Google is very afraid of misclicks of children when they use the phones of parents and problems associated with this. Therefore, such sales receive frequent rejections and a very high probability of getting banned for fraudulent actions.