On Safire devices with independent outputs the selection menus from which to operate remain on only one of the screens, the one chosen as the main one (typically the HDMI1).
However, you can switch the mouse control momentarily to the secondary video output if you want to reorganize the channel layout directly (without doing so through the internal menus).
We provide a demo in our Safire CCTV course and specifically in our certification course (minute 1:34:34):
https://youtu.be/QU3kgn0rBk4?t=5674