allout-plain-bullets-string is a variable defined in `allout.el'.
Its value is

  • Automatically becomes buffer-local when set.
  • This variable is safe as a file local variable if its value
    satisfies the predicate `stringp'.

The bullets normally used in outline topic prefixes.

See `allout-distinctive-bullets-string' for the other kind of

DO NOT include the close-square-bracket, `]', as a bullet.

Outline mode has to be reactivated in order for changes to the value
of this var to take effect.

You can customize this variable.