At this time, there is no way to accomplish what you are looking for. The only way to see all content in a Presentation would be to preview the Presentation, however that will adhere to durations that you have set for all content.
Please consider my question a feature request then. I feel like I'm designing blindfolded. Most of the duration settings in our presentations are 60 sec or more and it is not practical to change them globally every time I want to quickly preview a presentation.