As well as with the arrow keys normally used, the subject position in stereo-space may be altered from this menu option or all alignments may be reset.
By using 'Shift+ArrowKey' you can make adjustments of a single pixel.
The size of the pixel-step may be set in 'Edit/Preferences' and the default-value is four pixels.
The left and right alignments determine the position of the image with respect to the stereo window.

Put on your red/cyan glasses and view the above image, from the 'Easy Adjustment' section.
It can be seen that some objects 'violate' the window, that is they are in front of the screen.

This is the result after using the left and right adjustments to push the nearest object just below the window.