Hi @spaceshipone,
Thanks for getting in touch! Category-specific filtering is actually one of the many filtering options available as part of our Filter Bar add-on. If you’re interested in offering more complex search and filtering options to your users without writing any code, it’s a great little add-on that’s definitely worth considering! Our product page (linked above) has plenty of information and screenshots to get you started learning more about it, and I’d be happy to answer any questions you might have, as well.
Failing that, you also might consider taking a look at our Themer’s Guide to see if a template modification might get you where you need to go! We’re not able to provide detailed support for customizations such as these, but we’d be happy to point you in the right direction if you should have any specific questions as you go.
I hope that helps! Let me know if there’s anything else I can do to assist!