i worked with nivo a bit earlier this year and last, while the docs are very pretty and interactive - they are also outdated. you mostly have to dig through source code to figure out what you can and can't do. to do what you want, i believe you need to create a custom layer, then you add that to the charts layers array in the order you want it. you will also need to do some sorta math to tell it where on the x-axis to start a dark (or light bar) and how wide it is.
– HolyMolyFeb 07 '21 at 03:06