I'm trying to figure out a way to insert a shaded band in a plot window. The aim is to highlight various regions inside a plot, and hence couple it to an xline() and a color.
Picture attached for an example.

I presume there's a way to work with fill() and use a fixed ratio of the y-axis to maintain consistent height. But maybe there's an existing function I'm unaware about, or an alternative way of doing it?