I'm facing the same problem and found both this issue and https://bugs.chromium.org/p/chromium/issues/detail?id=328504

Timestamps definitely need some love — they're difficult to see on timeline, even more difficult to hover and get a tooltip over, and can't be navigated quickly.

I imagine I'm not the only one using timestamps to mark certain phases of a page load (time to interaction, time to first display, etc.). Right now it's difficult to see how those markers relate to the timeline graph. Does this spike in reflow fall within one or the other "category"?

If timestamps are moved to a dedicated-ish section, perhaps it'd be even possible to constrain timeline with them? For example, make selection in timeline up until certain marker, after, or between.

I'll look into it.

@kangax: did you consider using console.time and console.timeEnd for tti, ttd?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7906a007c41fccf1b0576193494c1f5f5147cf85

commit 7906a007c41fccf1b0576193494c1f5f5147cf85
Author: pfeldman <pfeldman@chromium.org>
Date: Mon Jun 27 14:40:16 2016

DevTools: render markers as circles on the main timeline.

BUG= 619594 

Review-Url: https://codereview.chromium.org/2080633002
Cr-Commit-Position: refs/heads/master@{#402175}

[modify] https://crrev.com/7906a007c41fccf1b0576193494c1f5f5147cf85/third_party/WebKit/LayoutTests/inspector/tracing/timeline-mark-timeline-expected.txt
[modify] https://crrev.com/7906a007c41fccf1b0576193494c1f5f5147cf85/third_party/WebKit/LayoutTests/inspector/tracing/timeline-time-stamp-expected.txt
[modify] https://crrev.com/7906a007c41fccf1b0576193494c1f5f5147cf85/third_party/WebKit/Source/devtools/front_end/timeline/TimelineFlameChart.js
[modify] https://crrev.com/7906a007c41fccf1b0576193494c1f5f5147cf85/third_party/WebKit/Source/devtools/front_end/timeline/TimelineUIUtils.js
[modify] https://crrev.com/7906a007c41fccf1b0576193494c1f5f5147cf85/third_party/WebKit/Source/devtools/front_end/ui_lazy/FlameChart.js

Hey @pfeldman, sorry I missed your earlier comment somehow!

I've used time/timeEnd but it doesn't really solve the issue, which is to see how certain app-specific events correspond to timeline events. For example, you find a spike in reflow in timeline and you want to make sure it falls under certain mark (e.g. tti — time to interaction — that many apps track). 

I'll check out your change once I get it in my canary.