Oh, right. I actually haven’t even gotten to the clip markers in the book yet (only Timeline).
But I tried this and you can’t see the marker moving while you are slipping. You only see the new placement after you release the mouse.
So it is not ideal. (Or maybe I am missing an option and need to read all the tutorials first 🙂
The clip marker does show up fine when moving a clip though, and it can be snapped to the playhead so there it works nicely. But after that both ends need to be adjusted (and it might interfere with neighboring clips).
Another way would be to use razor blade in the video where the desired action is, then remove either half of the clip, move the remaining clip aligning the cut point to the beat, and expand the clip to fill.
But simply seeing the playhead location frame while slipping would be way more simple. Option for that would probably be super easy to implement as well.