I think you can just add it to Control Centre, no need for shortcuts. I made an app for reading in the dark, minimising the amount of light hitting your eyeballs, but I'm still using the red color filter every night.

The app is overall darker and more "strict" with how it handles content (esp. images) though: https://untested.sonnet.io/Heart+of+Dorkness and midnight.sonnet.io

Overall, reduced the number of photons is a fun metric to play with when building something/messing with prototypes.