Changing Slide Show Interval in Preview

This question has been asked for years with each new release of macOS and the answer is the same: Not possible.

Hello Danny_Mac,

Thanks for choosing the Apple Support Communities. We understand you want to change how long it takes to move from one slide to another using the slide show feature of Preview. This is not currently a setting that can be changed, but we do welcome your feedback and feature requests here: Feedback - macOS - Apple

As an alternative, you can use Photos or iMovie and manipulate how long a slide plays when creating a slide show.

Create slideshows in Photos on Mac - Apple Support

Create a new iMovie project - Apple Support

We hope this helps.

Cheers!