I use Notmuch to manage my emails (and that’s just wonderfully fast) and use the Emacs frontend for it. But when I wanted to save attachements, it was not that easy to create folders. I had to exit the save, open a terminal, a dired or whatever create the folder… I use Helm for managing completion in emacs (and that’s a nice piece of software too).
To avoid that and with the help of Sacha Chua, I managed to add a shortcut in helm read file:
tags emacs helm notmuch