the variable ~deft-default-extension~. Replacing the value with ~"md"~, for example,
will change the default note format to markdown:
#+begin_src elisp
(setq deft-default-extension "md")
#+end_src
You may also want to alter the way titles and file names are automatically
created by editing ~deft-use-filename-as-title~ and/or ~deft-use-filter-string-for-filename~.
Further customization options can be found here: https://github.com/jrblevin/deft#other-customizations
** Note
It is [[https://github.com/hlissner/doom-emacs/pull/2845/commits/dce80a3c8032f5390f4e763e18a108d5f3f08772][not recommended]] to re-enable deft's buffer auto-save.