Hello! Just popping in to say that as far as I can tell, there is no solution to this problem within Squarespace right now. However, I recommend checking out Squarewebsites' Universal Filter. This bit of code costs $70 but comes with a wealth of resources in the form of developer support as well as user forums to help you install and modify it to fit your needs: https://www.squarewebsites.org/universal-filter
If you have zero experience coding (like me), you will definitely want to take advantage of the forums. I managed to create a filtering system that has many variables and can be organized exactly as I want just by reading through what others have done. But you can also ask questions and folks are helpful. The developer is very active in these forums too, and can provide more advanced help (like actually writing code for your specific needs) for what others say is a very reasonable cost.
Having built myself a professional portfolio site as well as my shop's e-commerce site, I've realized that Squarespace is great for really really simple sites, but doesn't come equipped with the functionality you want for e-commerce sites or sites that need to guide users through large amounts of information. That said, there is a whole industry build around addressing these concerns. My e-commerce site renews next March: I will be spending this time deciding if I really want to give next year's website budget to Squarespace (I love what Squarewebsites is doing but it annoys me that Squarespace charges me so much money for Advanced E-Commerce and I STILL need to purchase code to make my website functional). Even with the investments I've made in outside code, I may end up switching to a provider that supports most of what I need without having to purchase extra code and support (it looks like Shopify might be that provider).
Hope this helps!