Which functionality within Service Mapping allows you to create a map using existing data?

The Application Discovery feature is the correct answer as it allows you to create a map using existing data. This feature is designed to identify applications and their dependencies from the current infrastructure, making use of pre-existing data to create visual representations of services. With Application Discovery, organizations can automate the processes of mapping out how different elements of their IT environment interact with one another, thus providing a clear overview of application dependencies.

By leveraging existing data, Application Discovery helps in building accurate service maps that reflect the real-time state of an organization's applications and infrastructure. This enhances the understanding of service relationships and can significantly aid in troubleshooting, change management, and impact analysis.

The other options, while related to Service Mapping, do not focus specifically on the creation of maps from existing data. The Service Visualization feature is primarily used for viewing and interacting with existing service maps rather than creating them. Data Import functionality pertains to the uploading of new datasets into Service Mapping, and the Service Prediction model works on forecasting future service dependencies and needs rather than constructing maps from existing information.