Yes, we do support "edit a file and save back directly". The implementation is different from others and is a lot more efficient than other implementations.
Please make sure you have the latest FileManager 3.0 client installed. You should open a file for editing by double clicking on it within FileManager. After done, just save it. The file will be saved in cache and sync-ed back to the server. This way, to open and save a file is almost instant! Other companies' implementations could lock your applications for a long time.