LibreOffice was capable handling various margins in Writer page styles
already. Be it top, bottom, left, right, inner, outer margins, all working. A
missing piece was support for the gutter margin, which is used when priting
for binding: additional space on the left or at the top, which is nominally
not part of the relevant margin. This means that the Writer document model is
capable of reading this information from DOCX files, render such files
correctly, saving them to ODF and supporting them at the various other layers
of the LibreOffice technology (UI, UNO API, etc). Come and see how this work
is implemented, where are the still rough edges and how you can help.