How to set 3 displays as follows: primary, mirror of primary and secondary?

The current setup of my displays is as follows: I would like the 2nd Sony display to be a mirror of 3rd Dell display, while the 1st Samsung display should remain as separate secondary display. When I try to change 2nd Sony display into Mirror mode, the button Apply is grayed out: Is there a way to make it the way I want it to be?