Hi @Wing Fan WONG,
At present, there is no direct connector to index SharePoint Online Lists in Azure AI Search service. The current indexing options focus on SharePoint document libraries and indexing SharePoint Lists is specifically mentioned as not supported.
In order to index SharePoint List data, creating a custom solution with Microsoft Graph API might be an option. This approach involves deploying a connector that extracts data from SharePoint Lists and imports it into Azure AI Search. Although this requires additional development effort, it offers a customized solution to meet your specific requirements.
Kindly refer to below documentation for better understanding:
Index data from SharePoint document libraries
Hope this helps, please let us know if you have any further Queries.