The definition of mandatory add-ons are products that a company wants to automatically add to a product when ordered. For example, a customer might want to have screen protector and DEP as mandatory add-ons when ordering a phone. The add-ons will not be editable in the store or in the checkout and if it says included in the purchase there will be no extra cost for the user ordering the product.
View on product page in store:
View in checkout:
The mandatory add-on configuration is done by your partner, therefore reach out to them for further assistance if you are interested to look over the possibilities for you to add mandatory add-ons.