Github user yuri1969 commented on the issue:
https://github.com/apache/nifi/pull/2269
About that _close/done/ok_ button, currently the advanced UI is implemented
as an `iframe` inside `nfShell`. The close 'X' button is a part of to the
`nfShell`. So for closing down the advanced UI you need to close the `nfShell`
too. I guess it can be done by traversing to the `nfShell` via the standard
`window` object. Is this approach ok? Since it feels, it introduces another
coupling element.---
