decrease-left-margin is an interactive compiled Lisp function in `indent.el'.

It is bound to <C-down-mouse-2> <in> <decrease-left-margin>, <menu-bar> <edit> <props> <in> <decrease-left-margin>.

(decrease-left-margin FROM TO INC)

Make the left margin of the region smaller.
With no prefix argument, decrease the indentation by `standard-indent'.
A prefix arg (optional third arg INC noninteractively) specifies the amount
to change the margin by, in characters.
If `auto-fill-mode' is active, re-fill the region to fit the new margin.