I'm working on a video that has lots of little intricate things that are pointed out in the text. Arrows on screen definitely help in this specific case.
A super fast way to add graphical arrows in Final Cut Pro is to use the Windings 3 font. Yup, a font.
You can launch Font Book -which is in your applications folder- to see exactly what arrows are available but for basic ones use the FGHJKL keys.
Now you can manipulate them as you would any graphic. Resize, alter color, rotate, keyframe etc…