[To draw four or less horizontal reference lines]

Display the [Trend Graph] dialog and click [Contents]. Check a [Reference Line] to use and set the value for displaying and its color. (4 lines maximum)

[To draw five or more horizontal reference lines or vertical reference lines]
Reference lines can be displayed on the scale marks.
For more information, click here.
Example: Configure settings on the [Left] or [Bottom] tab window.

1. In the [Trend Graph] dialog, click [Other Settings] -> [Scale] and check [Set Scale Display].

    

2. Check [Scale] on the [Left] and [Bottom] tabs. Check [Grid Line] and set as necessary.
   
   
   

   Lines can also be drawn directly on the trend part.