In BikeCAD version 16, we have two options for displaying front and rear chainline. You can use the Derailleur section of the Drivetrain dialog box to select a specific cog in the rear and a specific chainring in the front and then in the General sub tab of the Stays (auxiliary view) tab in the Dimensions dialog box, you can show the front and rear chainline for the engaged chainrings and cogs. As you switch from one gear to the next, you can watch as the chainline for the engaged gears changes. You can also display the offset between the front and rear chainlines.
The second option is to ignore which gear the chain is engaged on and simply show the average chainline in the front and the average chainline in the rear. When a double chainring crankset is spec'd with a particular chainline, this average chainline is the dimension being referenced.