Presentations in CustomShow 6 can be imported into the new CustomShow, though the individual assets in each presentation will be flattened into a single image per slide.
Each slide will contain a single image element, which is then placed into the presentation owner's Media Library under the My Resources folder.
Any presentations imported from CustomShow 6 will store their resources in the Web Presentations folder which creates an individual sub-folder for each presentation.
Video resources from CustomShow 6 are an exception to this, and are imported into the new CustomShow as fully-functioning video resources. These resources are imported into each user's organization's Media Library, where they are accessible by all users.
The video files are stored in the Web Presentation Videos folder.