Change the layers position within its parent layer group by
increasing the index
of the layer by one if possible. This means
that the raised layer will be rendered before (or on below) of its sibling
layer to the right.
Examples
if(interactive()){
p <- l_plot()
l1 <- l_layer_rectangle(p, x=0:1, y=0:1)
l2 <- l_layer_oval(p, x=0:1, y=0:1, color='thistle')
l_aspect(p) <- 1
l_layer_lower(p, l2)
}