Ahh, got it. Actually, it looks like there isn't a great way to do this right now. I will pass this along to the team and see if we can come up with a quick and easy solution.
One thing that will work, but it's very hacky, is to use a Tabs Block and:
- Hide the Tabs Content
- Use the tabs menu to configure the state of the active vs. non-active tab (the same thing the Product Quantity Selection list does)
- Use "Set Product Quantity To" interactions on the tabs menu containers.
I'd say give that a try and maybe it's a viable workaround while we figure out how to add this feature?