This is a Zetteldeft expansion (see §2020-04-17-1605).

First off: I’d advise against keeping multiple sets of notes. A major idea of Zettelkasten is to generate structure within your collection of ideas, not erecting barriers between them. If you require some basic structure in your file system, configuring deft-recursive will allow you to sort notes in subdirectories within your deft-directory.

That said, there could be fringe cases where you want to keep notes separate. If Zettelkästen are what you want – the German plural of Zettelkasten – then you could configure something like the following with the help of the amazing hydra package.

Note that the result is really separate: linking between the two Zettelkästen is impossible. Furthermore, attempting to merge different Zettelkästen with timebased identifiers can lead to problems.

With those caveats out of the way, let’s look at some code. First, define two functions that change the deft-directory and then run deft-refresh.

(defun zd-a ()
  (interactive)
  (deft)
  (setq deft-directory "~/zd-a/")
  (deft-refresh))

(defun zd-b ()
  (deft)
  (interactive)
  (setq deft-directory "~/zd-b/")
  (deft-refresh))

If your Zettelkästen use different naming schemes, you can throw some additional setq’s in there.

Next, create a hydra for convenient swithcing between the two.

(defhydra zd-switch (:foreign-keys nil :exit t)
  "Switch between Deft directories.
"
  ("a" zd-a "Zetteldeft dir A")
  ("b" zd-b "Zetteldeft dir B")
  ("q" nil "Quit"))

If you have large sets of notes, deft-refresh can take a while. One way to speed things up is to temporarily increase Emacs’ garbage collection threshold.

(defun zd-dir-big ()
  (interactive)
  (let ((gc-cons-threshold most-positive-fixnum))
    (deft)
    (setq deft-directory "~/zd-big/")
    (deft-refresh)))

The above is inspired by and cribbed from a discussion at Zetteldeft’s Github.