If you set the course to Restricted navigation, the learner can use the built-in Menu to return to previously viewed slides. They can also see other slide titles in the Menu. But they can't click on the Menu to jump to a slide they haven't already viewed.
Restricted navigation also disables the NEXT button until the timeline ends.
This post has more info about ways to control the NEXT button, and it includes a demo file: https://community.articulate.com/discussions/articulate-storyline/tip-controlling-the-next-button-101
For future reference, here's the link to the Storyline User Guide: https://community.articulate.com/series/articulate-storyline-360
Thank you so much for your prompt and useful reply!
