I can add "Publisher" and "Catalog #" as many times as I want.
And if I fill in String1\\String2 manually and save it, it will be written as multiple tags. Just from the script it is not working.
I will have a closer look.
Edit:
Ok. It also works for me.
I have to do an additional step.
"Publisher" and "Catalog #" will not be written in multiple fields just by CRTL-S.
I have to open "Erweiterte Tags" and hit OK. Nothing else.
For Genre it works with CRTL-S. This maybe because Genre is in the left mask.