Thanks. But its not quite the same.
In case I have to push down a specific condition, ex: select * from baseview where xyz = 123, as http://apiendpoint?xyz=123, I would use @xyz as interpolation variable, in that case the JSON Datasource URL will be http://apiendpoint?xyz=@xyz. This works, but the scenario I mentioned is different. The API endpoint does not take the colum name as query parameter, instead it takes a generic "$filter" as a query parameter with complete where statement.
Is it possible to use @WHEREEXPRESSION with JSON data source?