Am I missing something? Why can't you have an arrowhead as an option when drawing a line. I suppose I could find a font that has arrows as part of the collection and use that but, c'mon, no arrowheads?
Personally, for Shapes, I use either Photoshop, or Illustrator. Titler's drawing capabilities are pretty limited, once one gets outside the realm of "simple" Shapes. However, that is usually what is required in a Title.
You can create an arrow with the line tool, and then add a Style to allow you to adjust the Stroke as needed.
For simple arrows, I just use either Wingdings, or Webdings, as you suggest.