In the Amazon Redshift data source template if table types are listed as only TABLE and VIEW as follows:
<table-types>TABLE, VIEW</table-types>
then spectrum tables will not be listed as data resides in S3 buckets which is external to Redshift Data Warehouse. Add 'EXTERNAL TABLE' to the <table-types> in the Amazon Redshift Template in order to view the Spectrum tables in the data source tree view:
<table-types>TABLE, VIEW, EXTERNAL TABLE</table-types>
After changing the data source template, re-save any existing data sources in the Information Designer for the changes to take effect. Any new data sources created will use this template by default.