I refer to Shopify's default discount rule for "Buy x Get Y". Shopify only allows to create one rule per store. Apparent, it cannot satisfy the requirements, as I have to apply the similar rules to other collections too.
Hence, do you know any App can achieve the same discount rule as Shopify does?
elaborate the rules I would like to achieve: Buy every 13 ice creams, it's 4 dollars off.
e.g. buy 7 pcs icecream (as screenshot 1), it costs 7 dollars
e.g. buy 14 pcs icecream (as screenshot2), it costs 10 dollars: 14-4 = 10
e.g. buy 26 pcs icecream (as screenshot3), it costs 18 dollars: 26-8=18
Attaching the photo for your reference.
App Selly has wholesale feature that can help you to offer quantity discount:
You can turn off the current automatic discount, then create multiple offers via Selly.
To offer discount for every 13 items, you should create a bundle of 13 items.
This way, if customers buy 15 items, they will get discount only on 13 items, while the other 2 items are at normal price.