Only "some" 2-letter commands? Try looking through ':help z' and ':help g'. Ctrl-key commands become really important in insert and command-line modes. And n

Only "some" 2-letter commands? Try looking through ':help z' and ':help g'. Ctrl-key commands become really important in insert and command-line modes. And not to nitpick, but when you speak of "command-mode functions (e.g. substitution)", I think you really mean command-line mode. Command mode is another name for normal mode. Please try not to confuse the new/prospective users.