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+1 - found this thread from a search. I thought this might be the kind of thing Sublime already had. Shame it doesn't!

Splitting the file pane into two sounds good. Files at the bottom, outline at the top. Would be useful to me if the outline pulled in the 'code folding' levels and was nested. And you could say "Show 1 level / 2 levels / 3 levels deep in the outline pane". I'd use this all the time.

This post is a duplicate of

Upvote that one too if this is important to you.

Completely agree! I'm relying on third party plugins at the moment, but they're completely different on OSX, Windows (and there doesn't seem to be one for Linux).

My use case is: I've written a really simple error handler in PHP, that beautifies PHP error messages and provides a HTML link which takes me straight to the file, line and column in Sublime.

I'd suggest following TextMate's format exactly (it's nice to have a standard), but use sublime: or subl: as the protocol. Maybe even a user preference to grab txmt URLs too, as a lot of debugging tools already use this.