It looks like you're trying to visualize hierarchical data dynamically based on the most common terms, but you're running into Vega's lack of looping/recursion support. Your idea of using a doughnut chart with nested sections or a Sankey/tree-like structure makes sense, but Kibana and Vega's built-in tools may not handle this adaptively.

A couple of suggestions:

• Have you considered pre-processing the data outside of Vega/Kibana to generate the hierarchy before visualization? A simple script could structure the data before feeding it in.
• If a direct Vega solution isn’t feasible, D3.js might offer more flexibility for recursive structures.

It’d be great to hear if others have found a way to handle this within Kibana/Vega itself.