I’m using Libre Office v6.2.3.2 (x64) on Windows 10. I want to present an Impress Slide Show using a presentation mouse, which works by transmitting PageDown and PageUp. Both these buttons on the presentation mouse produce the same behaviour in Impress Slide Shows - they advance the presentation by one slide. I also tried using my keyboard, and PageUp, PageDown, Ctrl+PageUp, Ctrl+PageDown, Left Arrow and Right Arrow all advance the presentation by one slide.
According to this help page
https://help.libreoffice.org/Impress/Shortcut_Keys_for_Impress
which details keyboard shortcuts for Impress, if there are no effects, then PageUp should display the previous slide. Also, Ctrl+PageUp should display the previous slide, irrespective of any effects.
How do I show the previous slide in Impress using the keyboard or, ideally, a presentation mouse? And/or is this a bug?