Okay, so here's a tricky one.
I need to apply a 50% discount on 4 specific items (makeup bags) when any other item in the store is added to the cart.
But the tricky part is that we're using Advanced Pre Order (APO) app to have partial payments in our store, with this we let users pay 50% in advance for all the items (excluding the 4 makeup bags); the problem is that the APO app creates a new product when an item is added to the cart with the partial payments selected. The thing is that the newly created item is "virtually" created, as it is only an item in the cart, but not a real one in the store or at the Shopify admin, how? I don't know, but that's how it is.
So, my first option was to create a collection with all the items (named "All store items") excluding the 4 makeup bags, so I could make a simple automatic Buy X get Y discount, making the following rule: Buy any item from the collection "All store items" and get any item from the collection "Makeup bags" 50% off.
That looks simple, right? But as the partial payments products are not real products created in Shopify, they won't get added to the collection "All store items", so the Makeup bags won't get the discount as the rule is not completed.
So, any thoughts on how to create a BOGO discount without the rule of having the first item on a specific collection? a Simple "Buy any item, and get the Makeup bag 50% off".