If you are panning and zooming your slides in PSE7, and you would like to visualize how the "End" red frame aligns with the "Start" green frame, hold down the Ctrl key while positioning your red frame on the slide. To instantly visualize the result of your P&Z in PSE, push the spacebar.
This convenient feature constitutes one of the reasons, when I have a large number of slides in my show, I continue to do my panning and zooming in PSE7 instead of keyframing in PRE7.*
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*When I am satisfied with all the P&Zs in the PSE slideshow, I "Send" the show to PRE7, where I've already got my audio and its beats on the Timeline.