The only way I'm aware of to get externals added to existing shows is to submit a data request. It would be nice if there was a streamlined process that would allow submitting missing ones. I often end up with IMDb ids, but I'd rather use TVmaze so I convert them first and that depends on the externals being present. I'd be happy to help fix up the missing data as I encounter it, but using the data thread feels heavy for just submitting missing external ids.
My preference would be for there to be a form that allow submitting external ids for mappings that have never been set to anything other than null, making data thread only required for dealing with errors.
