Cannot change the Game System that a Catalog is assigned to.
I am new to Battle Scribe. For testing and learning I created a copy of a Game System and catalog. The catalog was still assigned to the old Game System. I was able to change it by manually editing the .cat file and changing the GUID the catalog was pointing to.
This can be done (I can add a text box in the catalogue editor). But bear in mind changing this is risky business and could break data in bad ways….
You can probably hack the roster file with a text editor. The roster is an xml file. One of the first tags contain the "gameSystemId" UID.
No tested, but should work to some extent.
I've come across this as well. This would be useful in deal with edition changes, and would make it easier for users to experiment with files more easily.