Under Night Light, "<gui>Manual</gui>" entry is called "<gui>Manual Schedule</gui>" in GNOME 40
https://gitlab.gnome.org/GNOME/gnome-user-docs/-/blob/master/gnome-help/C/display-night-light.page#L46-48 says "Manual" two times. One time it's called a button:
<p>Under <gui>Schedule</gui>, select <gui>Sunset to Sunrise</gui> to
make the screen color follow the sunset and sunrise times for your location.
Select <gui>Manual</gui> to set the <gui>Times</gui> to a custom schedule.</p>
But seems like it is called "Manual Schedule" in gnome-control-center and that it is not a button.
So perhaps the information it outdated. Or perhaps it is so new i can't see it in the translation files.
Edited by Andre Klapper