It can only be used for file-based objects like documents or document collections where one of the files is a markdown file. Only a single markdown file will be rendered. The markdown syntax is slightly modified, you can e.g. refer to M-Files objects of the same Object type as the containing document by writing
#<ID> in the markdown link.
# Example File [This should reference an M-Files object of the same object type with the ID 27](#27).