Use case: I remember class name (Python, PHP, etc...), but I can't remember filename. How can I use "Goto symbol" to find my class in the whole project, not only in the current file, or myfile@MyClass?
Out of the box sublime doesnt do this. I have tried to do the same thing. Most likely because doing that would be similar to a global search. Which with a large project can get quite slow. I bet with some monkeying in the python code you could find how to extend it on a global level. To give you a starting point, I enable sublime.log_commands(True) in the console and watch for the commands that are used to do that search. Then try and find that implementation in the python scripts used by Sublime.
You should check out the ctags package. This is precisely what it exists for.
Is it possible to search for all symbols with the Ctags plug-in? Or just jump to a symbol that is being called in your code? I think Ctags just let's you jump to the symbol but you cannot search project-wide for a particular symbol. I could be wrong. If there is another plug-in that does this, I would be interested to hear about it.