Hi, a bit off track here but if you just need a line as a graph indicator instead of an arrow you could download Route Generator(free).
You can then put a background of your choice (still or video) and animate a line,
any thickness and colour, over it. This will generate a series of BMPs which you can import into SV as a “still image sequence” on the timeline…render as normal after that…it’s free and a nice tool to have, Pete.