MusicXML allows for margins and other layout elements to be placed in so-called ‘print' element, inside measures, to change the settings for a given system:
When used in the layout element, the system-layout element
defines a default appearance for all systems in the score.
When used in the print element, the system layout element
affects the appearance of the current system only. All
other systems use the default values provided in the
defaults element. If any child elements are missing from
the system-layout element in a print element, the values
from the defaults element are used there as well.