Does anyone knows if it's possible to create an external list from another external list? Is it possible to create an external list on SharePoint Online from an existing external list on SharePoint onPremise. Thanks for your help.
This MSDN article suggests it is possible to use Business Connectivity Services and External Lists using SharePoint Online. Although the article does not explicitly mention functionality specific to 365, it details that it is possible.
O365 would need network access to your on premise sharepoint instance. You would need to make sure your SharePoint on-premise is accessible from O365 and not behind an internal firewall.
You could create an external list from a web service, which could be another sharepoint list.
You may also need to allow anonymous access, (or at least test what access is required) depending on how users authenticate to your on premise farm.
This article might help and is more relevant https://support.office.com/en-gb/article/Make-an-External-List-from-a-SQL-Azure-table-with-Business-Connectivity-Services-and-Secure-Store-466f3809-fde7-41f2-87f7-77d9fdadfc95