If you go into the TRIRIGA project picker, child projects are not listed. As a result, there is no way to get into the context of a child project and manage it.
As a temporary fix, clear the child project’s “Project Name” value (a value seen in the System tab). The Project Container Context query was displaying only the parent project records and not the child projects. Moving forward, the issue has been resolved by changing the Data Scope of Project Container Context query to All Projects, in order to display both parent and child project records.