Hiding/Unhiding a slide in Keynote for iPadOS
I guess you mean skipping a slide during a presentation, i.e., the slide will be present, but will not be shown during the presentation. Here is how to do it in Keynote for iPadOS/iOS:


In the slide navigator: Tap the slide to select it, tap it again, then tap Skip Slide (or Unskip Slide to include it back again). You might need to tap ▶️, or rotate your device to see the Skip Slide/Unskip Slide command.
In the light table view: Tap to select a slide or select multiple slides, then tap the  (the Skip button) or  (the Unskip button) at the bottom of the screen.


The directions have been taken from the Apple Support pages for iOS and iPadOS