I am using UE 5.0.3 and Windows 11. I have 3 displays side by side. Each uses 1920x1080 I have the offsets mapped correctly 0x0, 1920x0, 3840x0.
Switchboard/nDisplay fails to utilize available screen space if each monitor does not have some kind of activity (open file/folder). Instead of launching across all three of our displays it will launch all the viewports stacked on top of each other. To circumvent this, I have opened a folder on each monitor so that each will be utilized when launching the application through Switchboard. I feel this may be some kind of bug but could there be some setting I am missing that just forces the viewports into the correct location?