Cannot stack file tabs only on the left side in the editor

I like dividing a screen into right and left halves while editing. In R2013.a, I was able to stack file tabs on the left side of the editor as the first image shown below.

However, in R2014b I can no longer display tabs only for the left half of the editor. Instead, they appear on the left side of both right and left editors as follows.

In addition, I would like to display all the files on the left side of the LEFT editor instead of the RIGHT editor (as in the first image). It seems R2014b displays all the file tabs on the left side of the RIGHT editor by default (as in the second image). Is there any way to display all file tabs only on the left side of the LEFT editor as in R2013a (or earlier version)?