Adding marks to Chrome's Timeline tool?

Use console.timeStamp(markName). See https://developers.google.com/web/tools/chrome-devtools/debug/console/track-executions#marking-the-timeline for reference.

console.time() and console.timeEnd() now show under Performance's Console section (next to Main, GPU, Network, etc.).

For example:

console.time('Hello world!');
console.time('Hi world!');
setTimeout(() => console.timeEnd('Hello world!'), 1000);
setTimeout(() => console.timeEnd('Hi world!'), 2000);

This looks like this: