It is 100% possible to add new custom post fields.
But the problem is for every time I add a new or select an old custom post field and type in the value and click add it gets bugged. The only way for me to add another one is to update the game and re-edit it again.
I guess you understand that this can be a big problem if you have a lot of data entry to do..
Could you please fix the bug, or give me a solution on how to fix it my self.