Define new key bindings with leader key prefix

(map! :leader
      (:prefix ("o" . "open")
       :desc "elfeed" "e" #'=rss))

Remap leader keys

Change alt key bindings:

;; Add to config.el
(setq doom-leader-alt-key "C-SPC"
      doom-localleader-alt-key "C-SPC m")

Top-level key bindings

Pop up scratch buffer: SPC x