Not that you can’t get it done with a Position2d but what you want might be easier achieved using any node that derives from the Control node as they have the rect_pivot_offset property
So in practice lets say you use a TextureRect
texture_rect.set_rotation_degrees(45)
var position = Vector2(0, texture_rect.get_size().x)
texture_rect.set_rect_pivot_offset(position)