Deneb is an amazing, and newly certified visual, in Power BI. It allows you to create heavily customised visualisations using Vega and Vega-Lite.
This video is shows you how to get started with Deneb and Vega-Lite, and how to create some basic, but pretty cool, custom visualisations.
The resources mentioned in this video:
Vega-Lite documentation - https://vega.github.io/vega-lite/
Kerry Kolosko's website - https://kerrykolosko.com/