Change inset legend attributes.
This option accepts object that has the keys anchor, x, y and step.
anchor decides the position of the legend. These anchors are available: top-left, top-right, bottom-left, bottom-right
x and y set the position of the legend based on the anchor.
step defines the max step the lagend has (e.g. If 2 set and legend has 3 legend item, the legend 2 columns).