How to show time/duration on seekbar

I would like this so our reviewers can tell us where items should come in for our animations. All of the resources we produce are translations, and we mainly use text and images timed to appear alongside audio. As the audio is completely different to the English originals, the translated text needs to appear and disappear at completely different times. I don't speak the languages, and without a timeline reviewers struggle to tell us where each line should come in. External timers don't help as they need to pause, jump back, etc to work it out. Manually inserting a custom solution for each slide and layer would be way too much work for what we need, also! Will submit a feature request, too :)