It is difficult to move a column beyond the columns that are currently visible without using the horizontal scroll. So as column are listed in the drop down it would be good to be able to reorder here. Could also implement the auto scrolling of the horizantal scroll when moving column beyond the visible scroll. Both would be good.
I am facing the very problem as well. The column movement must be intuitive while reordering - so preferably auto-scrolling of Horizontalbar scroll should be supported. I also agree if out of the box support is available for either of the ideas posted here would be good. Lack of support creates a huge usability issue for our customers.