Is this no longer available with the new viewer?
Presentations have actually been moved out into a dedicated app:
As far as the functionality in map viewer is concerned,
This functionality is currently only supported in Map Viewer Classic. It will be available in a future release of Map Viewer.
Create presentations—ArcGIS Online Help | Documentation
@JayHanson , while "presentations" are not available in the Map Viewer, a new and better option with improved functionality is the new "Exhibit" instant app.
See the blog at https://www.esri.com/arcgis-blog/products/instant-apps/mapping/introducing-exhibit/ or check out the doc at https://doc.arcgis.com/en/instant-apps/latest/create-apps/exhibit.htm