I've recently got into using FireBreath for some simple task: download a clicked url. Is there a built-in method or something else with which i can add the url to Chrome's native download queue? or at least load up a Save Link As.. dialog (that would be ok too)?
You can show a save dialog by using the native OS calls to do so; for example, on the Mac you'd use NSSavePanel. That won't hand the download off to the browser though, it would just give you a user-selected filename to download to. You'd still have to do the download yourself.
NPAPI doesn't have a way to tell the browser to start a download using its UI. That would be something that would be an extension API if it existed (and what you'd want to file a request for if it didn't), not part of NPAPI.