Thanks for you answers, alexp!!!
Normally one should import a previous session and add new files and folders to the old content.
How do I add new files and folders to the old content, because there's always an exception, when I try to use the provided folder from OnDoneImport2(..., NEROLib.NeroFolder pFolder,...) as the root folder for the isotrack object? Could you give me a short code sample, no matter which language...