Manually tracking is the only way as far as I know.
I had at one point in the past asked the same thing, and someone kindly made a script to track every storage/global storage lua call into a notepad document.. and over time you could possibly figure out every single storage in use..
But there was no way to know how complete it was.. and it was also slowed the server down to a crawl. xD
I gave up on that method after a day or so and just went and did it manually.
(I also ended up tracking all itemid's that were in use as well while I was at it)
Here's the thread in question!
Maybe it'll be helpful for you.
Reason for script. I write down all of the storage values I have used inside scripts, so I never have to worry about which ones are used and not used. My friend doesn't always write them into the text document though. And the random people that helped with the project in the past never did...
otland.net