In Nov 2019, someone asked the same question and the answer was that it was not possible. Was there any change about that?
I would like to modify an existing visualization that uses an index pattern and use a saved search instead. I looked at 2 objects, one using the index pattern and the other the saved search and I think it is safe to say that the only thing missing to be able to correctly modify it through the GUI is the savedSearchRefName attribute.
Other than that, kibanaSavedObjectMeta.searchSourceJSON and references are already modifiable.
So I think the 2020 question is: how can I add a savedSearchRefName to an existing vis?