The linked post does not contain a correct answer, cause the Catalog and Content view are not used to differentiate between SAP/customer objects or to group specific object types in different categories.
The Catalog View gives a view on the runtime objects of the database artifacts. The first level you see under this view is the schema to which the runtime objects are assigned. In case you create e.g. a table using DDL statement CREATE TABLE you see created runtime object for the table under the schema which was used in the statement (but the table is not visible in the Content view).
The Content View gives a view on the design time objects of e.g. database artifacts (and further static content) stored in the HANA repository (therefore the objects are also called repository objects). Under the Content View the design time objects are organized in packages (1 to n levels). The activation of a design time object for a database object leads to the creation of the runtime object in the specified database schema. So if you create e.g. a table via an hdbtable artifact (e.g. mypackage.test.TestTable.hdbtable) and activate it you can see in the Content view the design time object "TestTable.hdbtable" in package "mypackage.test" and in the Catalog view under the schema you defined in the design object the runtime object "mypackage.test::TestTable".
Regards,
Florian