The Trend Line drawing tool has several useful applications. It is predominantly used to manually draw lines illustrating trends in the market or associated indicators. It can also be used as arrows (there is an option to put an arrow on one or both ends) which are used to designate points of interest. To draw a trend line at 45-degree angle, keep the Shift key pressed while drawing.
In Appearance property dialog it is possible to change the appearance of a Trend Line:
Sets the color, opacity, thickness and style of a trend line.
Allows shift of style between Line, Ray and X-line.
In Shape properties dialog you can set precisely the position of the Trend Line’s end points on the price scale (by setting the price) and the time scale (by setting the bar number):
Allows for the precise placement of the trend line’s first point (Price 1) using a bar number and price.
Allows for the precise placement of the trend line’s second point (Price 2) using a bar number and price.
In View properties dialog you can switch displaying of a Trend Line on charts of different timeframes: