If you are wondering what Dimensions can be used to map and group data from any of your data sources made in a Funnel account, just navigate to the Dimensions tab in the left side navigation:
Scroll past your list of Custom Dimensions, and a list of all the native Dimensions will follow. These are the Dimensions that you can use to build your Custom Dimensions on!
Alternatively, you can use the Search function. Just type the data source type.