Hi there! Thanks so much for stopping by–happy to help you out today! 🙂
Is this an issue you’re experiencing on a current install of yours? If so, I’d encourage you to post a new thread to the appropriate forum for your product, whether that’s one of our premium forums here or our free user support forum over on WordPress.org.
Additional fields added in Events Calendar PRO can absolutely be used as filters with Filter Bar, yes! You can read more about configuring Filter Bar on our Knowledgebase here.
Our calendar navigation bar (including search) is one of our customizable template files as outlined in our Themer’s Guide–I highly recommend giving it a good read over, as it’s got plenty of great info to get you started on modifying templates!
I hope that helps to answer some of your questions! Let us know if there’s anything else we can do to assist!