Condition for multiple slides

I did this with variables. One way is to create 8 variables. Slide1, Slide2, Slide3, etc. Set the value of the variable to false. Then set a trigger to change each Slide variable to True either once the timeline starts or ends, depending on if you want to force the learner to sit through the whole slide or not.

If you bring them back to the original slide even after all Slides are viewed, then you can create a trigger for a next button. I would create a next button on the slide so you can have the trigger go to the next scene (or wherever you want it to go next) with the condition that Slide1 = true, Slide2=true, Slide3=true, etc. You can either display the next button or have the next button show up only if all Slides#=true.

Or you can display the next button, but I'd also create a layer that shows a pop-up box (a rectangle with text) alerting them that they have not viewed all content. I also create an X button on the pop-up that is set to hide the layer when clicked.

Hope that helps.