In Elements, diagramming is by default 'hierarchical', meaning that for any created diagram, you can select any of its boxes and create a 'child' diagram from that box. There is no limit to how many diagrams can exist in a hierarchy.
The entire hierarchy of diagrams is what we call a 'map'. When you create a new diagram, by default you are creatiing a single 'top' level diagram. If you "drill-down" on any of the activities within this top-level diagram, you are starting to create a hierarchy of diagrams - which you will see referred to from time to time as a "process map"
Create new diagram
In the main Elements Home app, select "Diagrams" from the left-hand menu
Click on the New diagram button to create a new diagram. You will have an option to choose different types.
In addition to the standard UPN diagrams, you can of course create maps from templates, diagrams for user journeys, ideation whiteboards and thanks to advances in AI, you can now also generate diagrams from text procedures, work instructions, transcripts, notes and even images and sketches.
If you have content in Visio format (or Lucidchart), you can also import directly as described here. This also allows you to take a photo of post-it notes on a wall and import them straight into sticky notes within a Diagram