Create a blank file.  Draw some walls.  Create a section viewport.  Edit the Section Style class so that it has a light fill and heavy line (such as 0.70mm).  In the Viewport's Advanced Properties > Display, set the Line Weight Scale to 1.  Set Vectorworks Preferences > Display > Navigation Graphics to "Best Compatibility."  Update the section viewport, and draw a line (either inside the annotations or not) and set it to the same thickness as for the Section Style class (the 0.70mm) as