I want to set up a sale where a customer can buy any one item from x collection and get all items from collection(s) y on sale. Shopify only allows for bogo style sales, not buy one get "all".
For a specific example: i want my sale to say "Buy any bag, get all keychains/pins at 20% off"
Does an app like this exist?
Growave has a very multifunctional rewards program, you can change settings and customize actions to your likings.