At an old startup attempt we once created a nested hierarchy metrics visualization chart that I later ended up calling Bookshelf Charts, as some of the boxes filled with with smaller boxes looked like a bookshelf (if you tilted your head 90 degrees). Something between FlameGraphs and Treemaps. We also picked “random” colors for aesthetics, but it was interactive enough so you could choose a heat map color for the plotted boxes (where red == bad).

The source code got lost ages ago, but here are some screenshots of bookshelf graphs applied to SQL plan node level execution metrics:

https://tanelpoder.com/posts/sql-plan-flamegraph-loop-row-co...