Starting with Tiki18, search results returned by LIST plugin can be aggregated and some fields optionally summed. Accepted arguments:

• fields: comma-separated list of field names to aggregate the results from. The values of these fields will determine the key by which results will be aggregated.
• totals: comma-separated list of field names to sum and display aggregated amount. These fields need to be numeric type fields.

This is not connected with Elasticsearch's aggregations framework. In Tiki these are still referred to as facets which dates from the ES v1 facets module. These can currently (Tiki 19) be used only in PluginCustomSearch.