I would like to be able to change the angle at the end of a curved line and not just the position of the end point. I used to have a similar tool in Adobe Illustrator. I find myself often wishing for something similar in GoodNotes. I would be able to draw a wider range of curves and I do not think it would be so difficult to implement. In addition to the small square icon that one can reposition, I would add a kind of thin line (directed like the tangent of the curve at the "square" point with, say, a circular icon at the end: moving the circle would change the angle of the curve (i.e. its tangent) at the point.