We already have the ?tracking path for this:
https://meta.discourse.org/unread?f=tracked → unread in categories you track and topic you track and tags you track
https://meta.discourse.org/new?f=tracked → new
https://meta.discourse.org/?f=tracked → everything
The support for the special param is there in core, there is just no UI to expose it. We only expose it in “teams”.