The thing is, the procedure is not as specifically encapsulated as one might think.
Compared to TWC, there isn't quite a process to hook into, no story.displayTiddler() to hijack.
So, the components that end up creating a tiddler are generic.
There is no underlying code that truly knows of "a tiddler in the story".
The code rather creates widgets, e.g. lists, transclusions, etc...
where the end result is a tiddler in the story
...but that's just one of the ways these things are used.
How to hook into all that is a good question.
There should possibly be another widget,
something equivalent to the link-catcher widget
Perhaps some MouseEventWidget which eventually traps mouse events and, in this case, wraps...
...so as to register that double-click event. This, of course, meanse that any such widget contained within another one of that kind would fire first and need an option to specify as to wether or not the mouse event is to bubble up the dom, whichever click or move etc. it recognizes.
Unfortunately, aside from the code, there currently isn't.
However, Jim and I are currently discussing how to best automate all that:
This would be tremendously important to help the likes of you, well, all uf us really,
to find core stuff and their relations ...and have a full-blown api documentation.
Best wishes, Tobias.