Global script, how is it created?

[ambalboa]

I would like to write a global script that would get a version number, increment it, and then sent that value back to set it to a project. I can do this using the Run Script action as a project step, but I think it would be best if I can set version numbers to different items by passing the version number value back and forth to the global script which would increment it by one.

How can I do this? Do I copy and paste my project script into the global script tab on Script Editor?