How to customize legend height?

It seems that a vertical legend switches to “scroll mode” once it reaches the ends of the Y-axis. (According to this) In my case though, there is a considerable amount of room above and below these points to accommodate for the axis ticks/labels and titles. So I would really like to be override this behavior. (We also use plotly when creating charts in print / PDF which leads to a similar problem.) Is this possible?