Answer
In principle they're the same underlying mechanism — the metadata carries over automatically on upgrade (you'll still see CF$_ prefixed columns in the generated _CFV/_CLV views), but the screen placement itself has to be redone through Page Designer rather than carrying over automatically. The Entity Configuration page is the Cloud-era replacement for the old Custom Fields and Custom Logical Unit screens. What's genuinely harder in Cloud/Aurena: there's no System Info panel (which used to show the database view/columns behind a form) and no PL/SQL Package Code screen, making it harder to reverse-engineer the correct SQL or expression syntax for a Select Statement/Expression-type field purely from the client; having actual development access to a Build Place environment (with Developer Studio, to browse database objects and test SQL directly) is close to essential for anything beyond the simplest custom attributes. Absent that, using a disposable/dummy Quick Report as a scratchpad to test SQL statements is a workable substitute, since Aurena itself has no built-in SQL Query Tool. Also watch for object-connection navigation paths that worked in Apps10/EE (chaining through several related entities) not necessarily carrying over identically in Cloud — verify any such multi-hop navigation you're relying on still works after migrating.