To get you started in SMP, have a look at properties.js script in the 'samples/complete' folder. It somewhat replicates the Selection Properties DUI element, but every value is clickable to create a filtered auto-playlist.
(Not that I have any idea how it works mind you, most the action seems to takes place in list.js and deciphering that is beyond me! )
Of course a new component, or new title formatting $link function that works throughout foobar, would be ideal. Incidentally, the three foo_textdisplay commands do still work for me, at least in my limited testing, including http: and mailto: links, and the odd menu command -
$if(%path%,$cmdlink(Next Track,main_next))$crlf()
$if(%artist%,$doclink(Discogs,'https://www.discogs.com/en/search/?q='$urlencode(%artist%)))$crlf()
$if(%album%,$doclink(Email,'mailto:someone@somewhere.com?subject='$urlencode(%album%)))$crlf()
Cheers