This example shows how display a vertical path and how to highlight this path with css styling.
Link to sequence explorer on github.
The data is obtained (and mapped to the required format) from the sunburst visualization example from Kerry Rodden.
It is easy to see the pros and cons of these two visualizations for this specific data set.
https://d3js.org/d3.v4.min.js
https://ee2dev.github.io/libs/sequence-explorer.v20.min.js