You could also export the SVG file from VideoScribe and remove the transparent paths using Illustrator or Inkscape and then bring your modified SVG back into VideoScribe. We have an article called Fill an image using the hand and you are basically looking to remove the bit that this article tells you how to create
Try changing the units of the SVG to pixels (px) in the Document properties in Inkscape.
Also make sure that the stroke width is set to pixels:
Save and reimport into VideoScribe. You still may get a bit of thickening but it will be less than before.
We have now released VideoScribe version 3.2.0 where any transparent strokes will be ignored during the morph so you will no longer see the black lines over images set to morph that have a transparent reveal stroke over them.
Download version 3.2.0 from your account page. | View Release Notes for v3.2.