This MDL application locates all lines on any displayed level that cross other lines on any displayed level.  With an interface toggle control set to "Add Vertex", then if both lines are within a user-specified elevation difference, then a common vertex is added at the intersection in both lines and the elevation of the common vertex is set to the interpolated z value of the first intersecting line.  If the two lines are outside the elevation tolerance then the intersection is flagged with a large circle.  If the toggle control is set to "Break Line" then the second intersecting line is broken and a gap of 3 times the sub-units is inserted.