The page panel lets you customize the size of a page. We call it workspace here. You can also change the size of the safe zone. The safe zone is the area that will always be visible on screens no matter the aspect ratio. Read more about page sizes and the safe zones.
Page audio can be set in this panel. Upload or select an audio file that way only play when the page is shown on screen.
Tools for designers can be activated here too. Turn on grids or guidelines and configure them here.