xrandr cannot find mode, but shows up in list

Question

How to set a custom resolution? I followed the instructions here, but xrandr cannot find the mode when I try to add it (I am using 1440x709 to test)

(for reference i am on a GTX 1050 Ti with NVIDIA driver 390.67)

Updated screenshot from terminal:

Answer 1

1. Only lower resolutions are allowed.
2. I needed sudo for newmode and addmode.
3. I edit the mode line, e. g. 1400x700_60.00 to 1400x700.
4. I wrote a sh script to set Resolution on each reboot.

Check with xrandr without Extension if addmode was successful.