Commander Mode in Romancing SaGa 3

The Core Video Games Forum
1

To use the Seven STar Sword Trick, I must acitivate commander mode. But how? I pressed all buttons in the formation screen but nothing will happen.
I have one more question: is it necessary to use concentration for this trick?

Thanks for any answer…

2

I think commander mode activates automatically when you enter combat with your main character out of the active party.