Sets GameDVR_HonorUserFSEBehaviorMode = 1. Companion to the built-in 'Disable Fullscreen Optimizations globally' tweak (which sets GameDVR_FSEBehaviorMode = 2). Without this flag Windows can ignore the FSE behaviour override; with it, your exclusive-fullscreen preference is actually honored. Safe.
MaxTweaks applies this tweak with one click and snapshots your original setting first, so you can revert it cleanly at any time. A System Restore point is offered before batch changes, and every tweak links to its official source.
Get MaxTweaksOfficial documentation: https://learn.microsoft.com/en-us/windows/win32/direct3darticles/dxgi-best-practices