You should have an active license for the Scripting module to see the Scripting category (which includes the Script element) in the Flow elements pane.
An active license will give you complete access to the scripting API. Therefore, information in the internal datasets (XMP), external datasets or databases is accessible through the scripts even though the Metadata module is not licensed. You can also define script expressions for certain properties of some of the flow elements (example: Job priority property for the Hold job flow element).
Please refer to the Switch Quick Start Guide for more information on how to license and activate this module.