I had looked for something like this in a recent round of optimization to get a feeling whether it's really worth it optimizing individual css selectors. What I

I had looked for something like this in a recent round of optimization to get a feeling whether it's really worth it optimizing individual css selectors. What I took from (old) articles was that it's generally not and the effects are too small to measure, but maybe they never expected to work on large DOMs with lots of css. What I'd really like is something that'll run a performance recording and allow me to step into it at any given time to see what HTML + CSS is currently in effect, those things have been the most annoying to debug when styles are applied while content is still being parsed and flex is resizing when new columns appear as nodes are added and causing layout shifts.