added preview data source note

Author: HeidiSteen

articles/search/search-import-data-portal.md

@@ -80,6 +80,8 @@ The wizard is organized into four main steps:
 
 The **Import data** wizard connects to an external [supported data source](search-indexer-overview.md#supported-data-sources) using the internal logic provided by Azure Cognitive Search indexers, which are equipped to sample the source, read metadata, crack documents to read content and structure, and serialize contents as JSON for subsequent import to Azure Cognitive Search.
 
+Not all preview data sources are guaranteed to be available in the wizard. Because each data source has the potential for introducing other changes downstream, a preview data source will only be added to the data sources list if it fully supports all of the experiences in the wizard, such as skillset definition and index schema inference.
+
 You can only import from a single table, database view, or equivalent data structure, however the structure can include hierarchical or nested substructures. For more information, see [How to model complex types](search-howto-complex-data-types.md).
 
 ### Skillset configuration in the wizard