How do I configure Vim to stay only in insert mode (modeless editing)?

You can set the ‘insertmode’ option to configure Vim to stay only in insert mode:

    :set insertmode

By setting this option, you can use Vim as a modeless editor. If you press the <Esc> key, Vim will not go to the normal mode. To execute a single normal mode command, you can press CTRL-O followed by the normal mode command. To execute more than one normal command, you can use CTRL-L followed by the commands. To return to insert mode, press the <Esc> key. To disable this option, reset the ‘insertmode’ option:

    :set noinsertmode

You can also start vim using the “evim” command or you can use “vim -y” to use Vim as a modeless editor. You can also start Vim in insert mode using the “:startinsert” ex command.