I'm assuming your tables are stored as CSV in Hive.
This is actually a bug in the import tool. DSS supports Hive complex types (arrays, maps, ...) but the import tool fails to set the proper setting. Go to the imported dataset settings, and in the CSV format parameters, set the "arrayMapFormat" parameter to Hive.
Save, go back to Explore, and you should see your complex types.
Thanks for reporting this!