Custom GUI for Timeline Clip

I've been looking for ways to create my custom GUI for a Timeline Playable.
According to this thread it shouldn't be currently possible. However, with the release of unity 2017.2 waveforms for audio tracks were introduced, indicating that it's possible to manipulate what is displayed within a track. Yet it still seems that such an API is not available to us yet (and have not seen something being mentioned on the release notes of 2017.3 either).

My question is, is there even a roundabout way to at least create some segments/lines within my playable track, so I can give feedback to the user about where in the timeline certain events can be activated? (for example I have a music track and want the user to be able to place an event every beat, so using a GUI to indicate where every beat is would be useful)