If we have many applications(packages) under "Applications" tab, it is

An application doesn't have a field to indicate its origin (whether it was created in the environment or imported). Once an application is imported it becomes an object within that environment; there's no memory of it being imported as opposed of being created, at the end, importing creates the object.

If you store all import and export logs in a specific location/account then that would be a good guide to determine what apps were created vs imported.

To quickly get a list of currently available export and import logs, following rules may prove handy

apply(fn!document,finddocumentsbyname(true(), "export-log"), "name")

apply(fn!document,finddocumentsbyname(true(), "import-log"), "name").

finddocumentsbyname() is available in the Custom Content Functions Plugin.