Summary:
Accessibility option "Hide Lightning Flashes" is missing in Bedrock Edition. This option was introduced into Java in snapshot 21w37a:
https://www.minecraft.net/article/minecraft-snapshot-21w37a

Added an accessibility option to stop the sky flashing during thunderstorms

Steps to reproduce:

1. Open settings.
2. Try finding the "Hide Lightning Flashes" option.

Observed results:
"Hide Lightning Flashes" option is missing.

Expected results:
"Hide Lightning Flashes" option is in the settings.

Screenshots:
Java