By default, sub-category should uses the folder that is used for category that sub-category belong to.
unfortunately, if not define path for subcategory, document will be stored in the root of Edocman. And if define the path, it will open a new folder in the category folder that subcategory belong to.
I think, it we will be better to save all documents of sub-categories in the bath of category that they are belong to, and not in the root directory..