slide navigator
The slide navigator is a vertical list of slide thumbnails that appears on the left side of the Keynote window in slide view. You can click thumbnails to jump to specific slides or drag them to reorganise your presentation.
In slide view you can do either of the following to show the slide navigator:
Pinch closed on the slide to reduce the zoom level to Fit, or smaller.
Tap the button showing the slide number in the top-left corner of the slide.