Aggregated Table - no options to select reference table in Manage aggregations

The standard implementation is to use a direct query data source for the raw table and have the aggregation be in import mode.  The point of aggregations is to avoid having to go back to the data source for the most common queries.

Most likely you will have to switch your tests to a SQL Server based data source.

If your data source is in import mode only then aggregation tables don't make that much sense (apart from the queries performing differently between the main table and the shadow table).  You can still implement the concept, but it is like with non-folding incremental refresh - you will only see half of the intended benefits.