With the new ArcGIS Dashboards release in April, users now have the opportunity to use Data Expressions! Using Arcade, you can now structure, manipulate and combine data for your Dashboarding visualization needs. Check out this video for a couple of examples of how data expressions can be used.

Here are some helpful links:
Introducing Data Expression in ArcGIS Dashboards (Blogpost): https://www.esri.com/arcgisblog/prod...
Creating Effective Data Expressions: https://doc.arcgis.com/en/dashboards/...
Examples to get started: https://github.com/Esri/arcadeexpres...