This registry entry controls the diameter of the path line "tubes". In version 4.0, path lines are drawn as solid tubes in OpenGL. If you zoom out of your part display, OpenGL may not draw these unless you increase their diameter size.
Entry Name: DrawArrowRadiusInMM
Entry Type: Real Number to specify the radius of your path lines in millimeters. The default value is 0.1.
See "Showing and Animating Path Lines" in the "Editing the CAD Display" chapter.