There are many circumstances in which you may wish to draw lines Parallel to a Trendline. One example is a price channel. Another is Action/Reaction Lines. See Disclaimer.
To start drawing a Parallel Trendline, press the
button, or choose Draw Parallel Trendline Here from the menu. Once you have chosen the options you prefer, draw the parallel Trendline by clicking on any point through which you want the line to pass (if you use the menu, the point on which you clicked for the menu will be used to draw the line).
If the line to which you are adding a Parallel is a Pitchfork, the new Parallel will be drawn as a Warning Line (unless you have chosen Automatically Extend in the Parallel dialog).