yanchor

Sets the text box's vertical position anchor This anchor binds the y position to the "top", "middle" or "bottom" of the annotation. For example, if y is set to 1, yref to "paper" and yanchor to "top" then the top-most portion of the annotation lines up with the top-most edge of the plotting area. If "auto", the anchor is equivalent to "middle" for data-referenced annotations or if there is an arrow, whereas for paper-referenced with no arrow, the anchor picked corresponds to the closest side. Default: auto.