Hi Omar,
now i had time to test the settings. If I use “Fixed quantities” it the steps are used for every product itself, but I need steps of 12 in cart in total. It does not care if there is just 1 of product A and 11 of product 2, in total we need 12 or steps of 12 in total cart.
There is a further option: “Cart Total Fixed Quantity Options”, but I can not activate it. Is it a Pro feature?
Thanks in advance, Florian