Describe the feature:
The remove processor has incorporated a keep option where you select a list of fields to keep and drop the rest, this enhancement was done here: elastic/elasticsearch#83665

Describe a specific use case for the feature:
Right now if you set the keep option in an ingest pipeline you won't see the option when editing the pipeline in the Ingest Pipeline UI in Kibana, so at the very least this should surface somehow in the UI when editing.