Try using a scaling value in combination with calc()

[rijkvanzanten]

F.e. this

:root {
  --margin-none: 0;
  --margin-small: 1em;
  --margin-medium: 2em;
  --margin-big: 3em;
}

el {
  margin: --margin-medium;
}

could be rewritten as

:root {
  --scale: 1;
}

el {
  margin: calc(2em * --scale);
}

That way, when editing the scale, you don't have to edit each version of the variable

[dandevri]

That's a really good tip! Only need to use one variable to change the whole whitespace of a document.