How do you know there are these codes in discord to replace it value? I'm new in code

[cyan-science]

--backdrop-overlay: --backdrop-image:
--backdrop-position:
--backdrop-size: --backdrop-repeat: --backdrop-attachment: --etc...

[Leozard]

these are variables not part of discord but are created by us. you can read more about it here https://developer.mozilla.org/en-US/docs/Web/CSS/Using_CSS_custom_properties

[cyan-science]

Thanks 👍