Code:
calibre, version 7.23.0
ERROR: Shorthand property not allowed: margin is a shorthand property. Use the full form of the property, for example, instead of font, use font-family, instead of margin, use margin-top, etc.
I would say 98% of the books I open to edit use shorthand margin in every case with very few exceptions. Is there some reason that this functionality couldn't be incorporated?