I have added a ERD module to WebDB, for producing simple little relationship diagrams like the one above. As with WebDB generally, it’s not about displaying the actual database schema but rather just a simple way to display the semantics of the schema (often, to users who don’t want to see even a single underscore!).
Initially, it selects all tables that are linked to at least one other table (either inwards or outwards), and then gives the user the option of hiding or showing each table.
I’m moving WebDB towards a modular structure, and one that can be installed with Packagist. Not there yet though.