I was surprised that there is no Pause button in the action buttons preinstalled in Powerpoint 365. There are the Previous and Next buttons, but not the Pause button. I searched the documentation and found nothing about it.
On the other hand, is it possible to force a presentation displayed in the viewer (Powerpoint Slideshow) to use the “View by a person” parameter so that the title bar with the Reduce, Enlarge and Close buttons are displayed in the viewer header? By default, the parameter used is “Presented by a presenter” which has the effect of displaying the presentation without the title bar and the buttons for Reduce, Enlarge and Close.