I want to use a script to control the visibility of the fog, but I did not find the string corresponding to the variable name on the Cloud and Sky page. I am using Unity 2018.2.8.
I believe I have answered your question by email, but for completeness:
Please see the section on Fog in our documentation: https://docs.simul.co/tutorials/sky/variables.html
I also quickly checked and these string values should be available to use:
Haze, HazeBaseKm, HazeScaleKm, GroundFog, FogCeilingKm, HazeEccentricity, MieRed, MieGreen, MieBlue.