As discussed in this UDN post, the GetSupportedFullScreenResolutions function does not currently return resolutions for all connected monitors, only the primary one.
Multi-monitor set-ups are fairly common for PC users, it would be really helpful if the built-in implementations could support this feature.
I implemented this years ago in PR https://github.com/EpicGames/UnrealEngine/pull/3962 which got backlogged and never integrated, not sure if it still works but it should be a good starting point
Thank you for sharing this! I probably don’t have time to set up a custom engine to integrate this but it’s nice to know other people are hitting this issue. Did you end up using this? Or some other solution?
I write is specifically to ship the game, so we did use it yes 
Unfortunately, the link is no longer valid and I would still be very interested in a solution. Is there a way to see the solution?
yea the primary-only thing is exactly why that feature request exists — GetSupportedFullScreenResolutions only reports primary.
for per-monitor supported/native res use GetMonitorByIndex(index)->NativeWidth/Height or loop GetAllMonitors and build your own dropdown. that way multi-monitor users get the right options per display instead of just primary. its exposed to BP now — Multi-Monitor Display Controller | Fab