This navigation panel appears when you have used a presentation template rather than a web template.
I am not aware of any method to remove this new feature from presentations.Slide navigation
On any slide of the Presentation on the Web if you move your mouse to the lower left corner of the browser window, you get a pop-up page navigation control that includes a menu of all slides, thus allowing direct jumping to any slide.
Previous, Home and Next controls as well as a pop-up menu showing all pages of a Presentation.
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