How do I restore Arrangements in System Pref/Display?

[blackxacto]

19,1 iMac 10.15.3, Thunderbolt 3 /Thunderbolt 2 Apple adapter+Thunderbolt 2 cable to 17,1 iMac 10.15.3. I just want to extend my 19,1 monitor onto the 17,1 monitor, and I need Arrangements to show in System Preferences/Display window, but it is not there on either iMac. I have no trouble screen sharing, I just cannot extend my main monitor to the older iMac as an extended display.

I am using the correct cable and cable adapter, both made by Apple.
Yes, I have rebooted both. Both appear in the left side finder window.
I shut down the iMac, unplugged the power cord, waited 30 secs, replugged the power cord and booted.

No Arrangement window. Anyone know how to extend my main screen to another iMac?

 

[blackxacto]

Does anybody extend their screen to a second iMac, using a new iMac like 19,1? I have spent all week trying to find a way to do it. Apple does not support it in a 19,1 iMac, even using a Thunderbolt 2 cable and a Apple adapter to Thunderbolt 3.

I do not want to screen share. I only want to extend my screen to a second iMac.

 

[blackxacto]

Duet allows me to extend my screen. But I am using Apple Adapter and Apple cable.