cd “C:\Program Files\Oracle\Virtualbox”
VBoxManage setextradata “Your Virtual Machine Name” VBoxInternal2/EfiGraphicsResolution X
1280x7201920x1080
2048×1080
2560×1440
3840×2160
1280×800
1280×1024
1440×900
1600×900
VirtualBox doesn’t support 1366×768 so you can use 1280×720 with “Scaled Mode”.