Hi @BruleeH ,
Welcome to Q&A forum!
There is no way to synchronize the workflow creation interface from SharePoint Server with SharePoint Online. However, you can use SharePoint Designer 2013 to create workflows for both SharePoint Server and SharePoint Online. SharePoint Designer 2013 can connect to any SharePoint Server site as long as you have permissions to that site and can access it over a network.
For your reference:
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