Not sure why you can't filter based on every attribute in the system, seems a little short-sighted. Specifically what I'm looking to do today is to recategorize tickets. I'd like to filter based on the subject so I can then do a bulk action on those tickets. Apparently that's not possible. You should change that.
I've complained about this exact issue.
Thank you for your feedback. We will add this to our backlog.
I shall provide an update when we prioritise this request.
Product @ Freshservice