...
The available external properties may not all be displayed, but you can simply search them by name.
...
For "String" and "Boolean" external properties
Only the count COUNT is available. It counts the number of external properties with a value.
...
You will need to manually refresh the aggregator to redo the calculation if you update the values of the external properties.
Changing the operator
Click on the cog in the aggregator cell to change the calculation type
You can also hide the totals if the default aggregation is not relevant.
...