I have never used it before, but it seems to work on my z fold 4. My Phone is up to date. For me I have to use two fingers.
In settings, I found it under advanced features>multi window>swipe for split screen
Unfortunately it is checked right now and has always been.
Danny
edit: Ok, I tried it with two fingers. I never had to use two before, but I guess I do now. Odd.
Thanks,
Danny