Phorge has 60+ databases with lot of tables. If you know a nice tool to display such complex situation, thank you for your proposal.

We don't maintain such a document, but you could build the schema by only following the "database" parts of the manual (getting the code and running ./bin/storage upgrade) and dumping the whole schema.
There's a "quickstart.sql" file that is sometimes created in this way - it's currently more-or-less up to date.

Then you can use any tool you have to view this schema...

I used MySQL Workbench to reverse engineer quickstart.sql and create diagrams for each DB, hopefully that's helpful. See my recent uploads for the SVGs.