I just noticed something, when waterfall is huge bandwith it's not showing any markers.
Not that tyhis matters as with many markers it would end up as yellow-block.
However, can you place for every marker a single yellow dot? Just a small dot.
So people see there area markers.
Clickable isn't needed if that causes problems, but just a dot. With many dots it will become a small line, with a few dots it will show where markers are.
As it takes some zooming before they show.