Good news, all tables can be accessed in a Hive notebook. One simply needs to keep in mind that different connections correspond to different namespaces.
To access table foo from another connection, prefix its name by the database name (for instance “db_bar”):
SELECT count(*) FROM db_bar.foo
Note that you'll need to remove the prefix when converting to a recipe. The database name is shown above the sql code area: «connected to db_bar (Hive)» and is distinct from the connection name.
You can also find all database names by executing the SQL query
Note: you might also check the metastore sync: open the dataset, click settings → advanced → metastore: Synchronize.