Not sure if this is supposed to be like this, but I found 'Slide 1', 'Slide 2' etc. to be much more helpful than having the same 'No title' for all.
Bonus UX fix: Add pointer-events: none; to tooltips. This makes it easier to use whatever the tooltip covers, and you cannot select the tooltip as an element of the page.
1. If no slide title is given use Slide 1, 2, 3 etc.
2. It should not be possible to hover or select the toolip – this makes it hard to hit whatever is behind it.