Seconded. I am not a fan of the default margins and find it to be a slight annoyance that I have to switch them to 1-inch every time I make a document.
Hello,
You can locate the empty files (new.docx/new.xlsx/new.pptx) for every locale at
/opt/onlyoffice/desktopeditors/converter/empty
C:\Program Files\ONLYOFFICE\DesktopEditors\converter\empty
and set your own settings for the default files.