Not sure how this works, so I'll just type the suggestions.
Make the scroll bars in the Windows app larger. The one for the content, make both wider and taller. It is too small to accurately locate the mouse on it. I'm old fashion and have never owned a "scroll wheel" mouse, preferring touchscreens, touchpads, and normal two button mice. For these devices, what is provided is very difficult to use. For the scroll bar for slide previews, it is "long" enough (longitudinally) but again is not wide enough. Anyway, the developer is assuming scroll wheel operation I believe.
Offer the Left / Right arrows when on air as quick screens and either use the extra space for larger slide previews or whatever might be useful.
Thanks in advance for your consideration!