This video walks through a short sample add-on to give you a jump start in trying specific platform features.
Making progress (bars) with Slides Add-ons
Google Slides doesn't have progress bars. Wouldn't this be a useful feature for both presenters as well as audiences? In this video, developers learn how to implement simple progress bars by using the Slides Service to create an add-on. With this add-on, users can enable or hide progress bars in their presentations. The code and a full description of this add-on can be found in the documentation as a Quickstart example.
(Running time: 4:12)
This feature is also described in the blog post “Making progress (bars) with Slides Add-ons”.