Well, I use the Link feature with a button in the prior version to link to other pages. This is now consolidated into the revamped hotspot feature.

I've used this on a single project so far to show off interactivity by creating a mockup, duplicating it, adding in the interactivity changes (say, a popup or other state changes), and then create a button to link off to the duplicated page with the extras. It made for a pretty nice mockup with demo-ability.

The current version has moved this into the hotspot feature, which appears to allow arbitrary hotspot creation and the same ability to link to other mockup pages. There is now no need for a button as far as I can tell.