Switching from Direct Query to Import for Parametirized Data Source

I am experiencing an issue when having to switch from Direct Query to Import mode on an existing data source. The Query is using parametarized Server and Databse Name, which were set-up in the Advanced Query editor.

When wanting to edit the Data Source from the first query step, in order to switch from Direct Query to Import, I get an alert message of the ServerName and DatabaseName not being filled in. Thus I can not save the changes to Import, and being stuck with Direct Query.

Is there a way to switch from direct query to import, not from the Query Step setting itself?