Create subfolders under each folder in the document section of a file

Whenever we receive a new case, we create its respective "File". Once we begin to receive documents related to the case, we save them in the File under "Documents". We use the folder system to sort each document into its correct category ("pleadings", "witnesses", "correspondence", etc.). However, it is currently impossible to create subfolders for each of these (for example, under "witnesses" we would like to be able to create a subfolder for each witness and their documents). Adding this feature would significantly upgrade Amicus' organizational capabilities. Thank you.