Is there any way to allow learners to toggle automatic advancement and playof slides on and off?

The only way I think you would be able to do this is create a Boolean variable, for example autoProgress = true/false. Allow the user to toggle this variable. You would then need to add an if statement to your slide such as:

On slide timeline end > If autoProgress equals True > Goto next slide.

Therefore if autoProgress is false, the slide will not progress. It's a bit more work on your side, but you may be able to put the trigger in a master slide depending on your project structure.