Hello! Just wondering if anyone could help with this problem:
We are currently building a Shopify store for a client. A Christmas Product will be sold with an additional and optional two products. So, the Christmas Product is live and on the shopfront, but the other are optional extras. These extras cannot be purchased separately and a customer can only order up to 2 per Christmas Product, not per order.
My problem – I have tried doing this with Shopify Bundles and putting the product with the extras in a ‘set’, but you cannot set an option for a quantity of ‘0’; meaning if the customer does not want the extras is not an option. How could I make ‘0’ an option?
Any help would be great, many thanks in advance.
I think you can pass Add-on qty as ‘0’ in shopify but would the order be placed If the Add-on qty is ‘0’.
Hope you understood what I am trying to convey.
Hello.
I’m Max - Support representative at Seal Subscriptions.
This would be possible using the free Bundler - Product bundles app and another quick workaround in tandem with it.
Firstly, install the Bundler app and create your desired bundle.
Next, follow this Shopify guide on hiding the add to cart button on products: https://help.shopify.com/en/manual/online-store/themes/customizing-themes/hide-add-to-cart-buttons.
Let me know, if you have any further questions. 
I’m having this same problem, and the response from SealSubs-Max does not address it.
We want to have an optional item in a bundle. Basically another dropdown with “no widget” / “include widget for +$60”. The bundle app doesn’t seem to have this ability. We could add the option on the source product, but that would mean it would still show up on a pack list which will be a problem with fulfillment operations.