How to set the resolution?

I want to set the game resolution in full screen mode, similar to “Red Alert” and “Legend”. For example, if my screen is 1920 * 1080 and I set the resolution to 800 * 600, then the game will still be in full screen mode, with only the middle 800 * 600 being the game content and the rest being the black excess. How should I set it up?

From my understanding, it seems that the Unreal Engine 5 only has two modes: full screen and windowed. I’m not sure if this can be set or if I need to customize the rendering mode of GameViewportClient. Thank you everyone!

The following code is for switching modes and changing the operating system resolution, rather than the specified resolution in full screen mode:

r.SetRes 800x600f
r.FullScreenMode 0