This is a (I believe) non existing feature I would love my browser to have in order to help my open links in the background Diogenes syndrome.
I call it “referral feature”: bring it up and it would tell you how the hell you ended up on that mysterious tab you are looking at right now. A proposed location within the browser IA is behind its window title bar, and a desirable trigger could be ⌥ + click on title bar, emulating the cmd + click used to access to parent location on standard Cocoa apps. Ideally, it would interconnect with other applications so it could deep trace (and link to) obscure referrals such as a link within a Twitter DM you read through the Twitter app.
The really quick mockup that follows pictures a realistic proposal for its GUI:
