All later build revisions have built-in hardware based ComfortView Plus. So there was no need to have Menu- Color- Preset Modes- ComfortView. All of the online User's Guides will be updated to show = ComfortView: Decreases the level of blue light emitted from the screen to make viewing more comfortable for your eyes. This option is not available when your monitor comes with ComfortView Plus.      
I bought a Dell S2721DS on June 13th, 2021. It has ComfortView option under Preset Modes and I really like this option as it helps eye strain. I ordered another S2721DS on December 2nd, 2022 but it doesn't have the ComfortView option. Why is this option missing?
S2721DS, new, missing Preset ComfortView option?