Comfortlight Pro isn’t offered on the Kobo Glo or the Glo HD.
From:
https://help.kobo.com/hc/en-us/artic...een-brightness
About ComfortLight PRO
ComfortLight PRO is a feature that adjusts the screen’s blue and red light to make reading easier on your eyes. During the day, the screen displays a small amount of blue light to keep you alert. As the day progresses, the light gradually changes to an orange candlelight, and contains less blue so that the blue light doesn’t affect your sleep.
ComfortLight PRO is available on:
Kobo Libra H2O
Kobo Forma
Kobo Clara HD
Kobo Aura H2O Edition 2
Kobo Aura ONE