Setting up Dual imac Screens
I have a 2013 imac running on OS X Ver 10.9.5 that I wanted to use as a dual screen and a 2020 macOS Big Sur Ver 11.7.4 that will be my primary screen. The command + F2 or FN + F2 does not toggle to see both displays, only the brightness on the standard F2 command button. I also can't see the "arrangement" tab under the display. How do I setup dual screens for these 2 imacs? I'm using a apple thunderbolt 3 (USB-C) to Thunderbolt 2 adapter, with a thunderbolt 2 cable.
iMac 27″