Connect two 2017 iMacs through thunderbolt 3

Is it possible to use a 2017 21.5 as the secondary monitor to a 2017 21.5 retina 4k. I am aware you can share a mouse and keyboard between the two, but I'm unable to drag windows from one screen to the other. I've only found 1 video stating to connect a thunderbolt 2 to a thunderbolt 3 by selecting CMD F2 on the 2nd keyboard but this doesn't appear to work for two thunderbolt 3 connectors. Any help is appreciated.