Update or chance Source channel in PipeDrive

Hi all!. I am working on a client that currently uses PipeDrive, but for some reason the field Source channel seems to not be found in any of the outputs I get form get a Deal.

I checked everywhere and I could not find a way to edit that. Could not even find it in the API documentation. Any advice? I would normally just create a custom field, but my current’s tier in Pipedrive does not allow to use the Insight (dashboard) with custom fields