You could just select all the code and use SHIFT+TAB or EditOutdent.

Mind you isn't it easier to follow code that is well indented?

If the problem is that it's badly indented then there are add-ins that
can help.

Personally if I have to deal with badly indented code I just remove
all the indentation and then redo it.

Sometimes that actually helps, for me anyway, in understanding the
flow/structure.