You can’t because “Repository” is not a field of Source record. The link between Repository and Source is “intermediated” by “reference record”, implementing the 1-to-many relationship. The reference record is displayed as side information on individual source or repository record.
The configuration dialog gives access only to the primary fields of the record.
To list sources pertaining to a single repository, use a filter.
Thanks. I guess that makes sense in the ‘domain’, since the same source may be in multiple repositories
I’m familiar with entity relationship diagrams for RDB schema, showing PKs, FKs and join tables in a case like this. When I looked at the structure of a GRAMPS database exported to SQLite, I saw some obvious join tables, and thought of producing the sort of entity relationship diagram I mentioned.