Here is an example using the default data in a Create Data node that aggregates data grouped by the 'type' field's value.
You can initially use the grid editor to generate the individual aggregate values:

Which generates the following output:

Then you need to switch to the Advanced tab of the 'Operations' property. The metadata for the additional fields you want to output are configured in the ConfigureFields script (in the example the 'color' field is being output).
To create a new calculated field you need to define the metadata in the ConfigureFields script (here the 'Total' field being defined as a Python float type - which equates to a double)
The value for the 'Total' field in this case is the sum of the individual aggregate values

Which generates the following output data:
