Upload new version of personas global script

Hi,

I use a global script resource in Personas and in my Flavor I reference it via it's GUID. If I need to make changes to this global script, how do I do that in the admin transaction. I don't see how to upload a new version of the script and keep the GUID the same?

It feels like I am missing something very obvious. So apologies in advance for the stupid question!

Thanks in advance,
Simon