I have the two machines connected via thunderbolt 2 (late 2015) to thunderbolt 3 (2017) and when opening the Displays in System Preferences, the arrangement tab does not appear. Do I need a specific cord for this to work?
iMac 27″, macOS 10.15
Use your iMac as a display with Target Display Mode - Apple Support
You can connect any of these older iMac models to another Mac from 2019 or earlier for use as an external display. Learn how to identify your iMac model.
Target display mode requires macOS High Sierra or earlier on the iMac used as the external display. It does not work with macOS Mojave or later.
Use your iMac as a display with Target Display Mode - Apple Support
You can connect any of these older iMac models to another Mac from 2019 or earlier for use as an external display. Learn how to identify your iMac model.
Target display mode requires macOS High Sierra or earlier on the iMac used as the external display. It does not work with macOS Mojave or later.
I'm not looking for an external display, I'm looking to use as an extended display, or like a second screen.
I was able to use a PC as an extended display with both Macs, but I'm looking to use both Macs together as 1 extended screen.
Apple does make the distinction. The link tells you the essential answer to your question which is that your model cannot be used as an external display (which is the same as a monitor, btw.)
I'm not looking for an external display, I'm looking to use as an extended display...
Same thing actually. :)
Can I use a late 2015 iMac as an extended monitor display with a 2017 iMac?
