User feedback in Navigator?

There is no good way to do any custom user feedback in Navigator. In general, Navigator doesn’t aim to be a ui framework, for that type of stuff you are better off building your own UI based on the JSON API and the JavaScript client libraries. The getting started guide walks you through a simple example.

As for viewing debug messages, take a look at How can I make debug statements visible in the sandbox logs? - #2 by cocreature. However, that still won’t make them available in navigator.