Userscripts.org

I just wanted to know the storage location of the notes. It would be interesting if they could be automatically backed up and taken to another computer for instance. This could be achieved if they were stored in bookmarks...

But I haven't got the slightest idea where they're stored. Any enlightenment?

a GM script can store values only in the user wide configuration file which you see when you access about:config. moreover it can alter only entries of one particular kind. this is done for security purposes else someone may write a script to alter your history, bookmarks, settings, etc.

for backing up you may try OPIE type extensions or just back up your user.js file ... even better keep a back up of your entire firefox directory via a automated method. for syncing i guess you may set up weave for backing up configuration though i am not sure it works.