Maybe if you post your Computer hardware including Make & Model of your Motherboard, CPU/APU, GPU card and Windows Version installed you might get more replies.
Does the AMD Radeon Settings have "Advance Settings" showing?
In the older versions of Radeon settings if you had Remote Play under Relive Game Streaming enabled the Eyefinity Tab would not show. But once you disable that feature the Eyefinity Tab will start showing up.
Another User found this workaround in this AMD thread: https://community.amd.com/t5/drivers-software/eyefinity-advanced-setup-missing/td-p/115311
Re: Eyefinity Advanced Setup missing
yes this works! thanks!
I also found another way to get this working:
Run "C:\Program Files\AMD\CNext\CNext\EyefinityPro.exe"
This opens a tool that pretty much allows you to set Eyefinity up as well, with the advanced options as well.