Discoverability of that button could stand to be improved. There's no label at all. It's definitely been helpful me to have it there, I just don't know how anyone not reading the forum would be expected to find it.

If you add some actual buttons, it would be nice to be able to manually adjust the range (on both axes). Maybe add buttons "autoscale", "more frames," "fewer frames," "expand scale", "reduce scale." If you want icons, I've seen buttons for increasing/decreasing the scale using a magnifying glass with a + or - sign.