FS#2421 - Make the preview of Shorten (LE) more visible
Andrew,
When we use Lengthen/Shorten (LE) with a positive amount the result is clearly visible when indicating a side of an entity.
With a negative amount there is seemingly no preview.
It is generated and shown but one can not distinguish it especially with solid lines.
Adding an orthogonal auxiliary preview shape some N pixels long would do the trick. 
Regards,
CVH