How can I diagnose Babel performance impact of individual plugins and presets?

I want to measure how each Babel plugin or preset contributes to overall build time in order to identify optimization opportunities. The process must allow me to establish a reliable baseline, isolate the effect of single items, and account for monorepo configurations where Babel may need to locate the root configuration.

What approach yields a consistent baseline build time for my current Babel setup? How can I safely disable a single plugin or preset to measure its impact without breaking the build? In a monorepo, what configuration or flag ensures Babel uses the correct root config during these measurements?