How to make a custom resolution in Ubuntu Linux 20.04

Hi,
I made a custom resolution using the nvidia control panel under windows (3840x4320). But I don’t know how to do it in Ubuntu 20.04. Can someone give clear instructions n how to do this? I have a NVidia 2080Ti.
The nvidia-settings application doesn’t seem to allow me to do it.

nvidia-settings
X server display configuration
Advanced…
ViewPortIn: (enter resolution)
Apply.