left-margin

left-margin is a variable defined in `C source code'.
Its value is
0

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

Documentation:
Column for the default `indent-line-function' to indent to.
Linefeed indents to this column in Fundamental mode.

You can customize this variable.