The three dots next to search results provide a great oppunity for bang discovery. I'd imagine most people don't really use the unofficial bangs explorer, and even if they do, this would be faster in most situations.
I'd imagine another dotted line followed by an entry called "Bangs for this website" and a slightly indented list of said bangs would work well..
Custom bangs can probably be ignored or at most added a later time, as discoverability for your own bangs is hardly needed.
