Add countdown timer in presenter view
If I am giving, for example, a 30 minute presentation, a count-down timer tells me how much more time I have left (e.g., 5 minutes). If I also know that I have 10 slides left, I know that I have 2 minutes per slide.
The presentation view currently only has a count-up timer. A countdown timer that keeps counting (e.g., in red) after it gets to zero (so you also know how long you are currently going over if you do go over) would be a lifesaver.