I recently want to construct a mediashow contaning over 100 slides. It showed the history of a nature reserve from 150 million years ago until the present day.
Organizing the large number of slides was problematic until I used sub-shows. Each era of 10 or so slides was made into a separate mediashow each with its own medialist. I then made a top level mediashow which had all the individual shows as sub-shows.
Each of the sub-shows can have show-text to describe the era; this is displayed on all slides in the sub-show.
When preparing the show I found it annoying to skip through a large number of slides to check the order of the later slides. I solved this by using the medialist for the top level show in a menushow, then all the different sub-shows became items in a menu.