Markdown block [..] could serve as analog to @link and could be added easily. However, this change could break some entries that are not meant to be links because these brackets could appear for another purposes, like

type
TR = record
  // [optional]
  a: byte;
  b: byte;
end;

However, only standalone blocks will be affected, that is, array item declarations arr[idx] won't.
Using another block signatures would break sync with [..](..) block defining an URL and bring confusion.
Any ideas?

My opinion: Do it. Affected range is quite low and PasDoc will emit warnings on non-found links.