changing resolution

hi there folks
unreal engine newbie here.
just wanted to know how can i change the resolution in a windowed fullscreen mode to any thing lower than the monitor native (1080P).
for example if i use r.setres 1280x720wf it should set the res to 1280x720 and then fill it in the screen
but for some reason it doesnt change rather it keeps the native one 1080p.

You can put it in full screen mode, but change the screen percentage

thanks ill keep that in mind also is there a way change the aspect ratio like 16:10 4:3 etc …

Not that I know of…