;; za: Toggle first level like outline-toggle-children.
;; zc: Hide complete subtree.
;; zm: Show only root notes.
;; zo: Show current node like "za".
;; zr: Show everything.
;; "ze" 'outline-hide-entry
;; "zE" 'outline-show-entry
;; "zl" 'outline-hide-leaves
;; "zb" 'outline-show-branches
;; "zo" 'outline-hide-other
"zB"'outline-hide-body; Hide all bodies, Emacs has "C-c C-t".
"zb"'outline-hide-entry; Hide current body, Emacs has "C-c C-c".
"ze"'outline-show-entry; Show current body only, not subtree, reverse of outline-hide-entry, Emacs has "C-c C-e".
"zl"'outline-hide-leaves; Like `outline-hide-body' but for current subtree only, Emacs has "C-c C-l".
"zK"'outline-show-branches; Show all children recursively but no body. Emacs has "C-c C-k".
"zk"'outline-show-children; Direct children only unlike `outline-show-branches', and no content unlike `outline-show-entry' and `outline-toggle-children'. Emacs has "C-c TAB".
"zp"'outline-hide-other; Hide all nodes and bodies except current body. Emacs has "C-c C-o".
;; outline-hide-sublevels ; q ; Is it any different from `outline-hide-body'?
;; outline-hide-subtree ; Emacs has "C-c C-d", Evil has default "zc".
;; outline-show-subtree ; Emacs has "C-c C-s", Evil has default "zO".
;; TODO: To mark subtree ("C-c @"), we would need to define a tree object.