That's what I do now. And that's not helping when I try to sync gameplay, camera, another PC's gameplay and another person's camera. Also I don't need to sync audio and that is usually desynced with video to begin with cause of NDI delay for separate sources. Marking all of those would greatly help.
FWIW, I use simhub that create a webpage that is just a running time clock that gets included in a group with the recorded dashboard/cams/etc and the clock sync and have to use that to sync currently. It's the best I've been able to do so far, but having synchronized chapter marks in each recording would be ideal.
Also being able to have the recordings split, which currently the main recording does, but not the source-record ones, would halso help to get clips and sections into more relevant files/sections, but still even in the file splitting, markers would be important.. (Yet? fingers crossed )
these have the time stamp sync in the top right:
The dash in the bottom right has only hundredths of second resolution, but could be thousandths like the other recordings:
In the actual stream scene, those get cropped out, so it's basically only internal in the recording.