I recently upgraded from 2019.1.1 to 2019.1.4 and calculated field is no longer available in aggregate field. Was this functionality taken out?
Calculated fields in aggregate steps that were created in previous version of Prep seem to work however this option is no longer showing for any new nodes created for aggregation nor can you add any additional calculated fields to aggregate nodes that already have calculated fields.
I don't see this listed on known issues anywhere.
Aggregate node from a flow created in 2019.1.1 with calculated field still working in 2019.1.4