Garmin Varia UT800 how to manually change the intensity of the light modes?

Hi,
Recently, I bought a Garmin Varia UT800 headlight with Garmin Edge 830. Mostly, I ride during the day and I want to use the day flash mode because it lasts around 25 hours. Unfortunately, this mode is too strong for city traffic. Do you know if it is possible to lower the intensity instead of changing the mode? Additionally, can someone tell me:
  1. Does Automatic Beam Intensity affect day flash mode?
  2. What is the difference between light mode auto and trail?
  3. Can I customize light intensity using the Individual light mode? I don't see any options in my Garmin Edge after selecting this option.
Thank you!