UViewport and FUMGViewportClient

Hi all!
I’m browsing around for some unrelated thing and Iook what comes forward:

Viewports in UMG widgets. This would have came sooo handy before for me. Of course it doesn’t show up in the widget palette in the UMG editor in a vanilla engine. Did anybody had a go with it? Is there more info about it? Why is it experimental since 2014? (first commit on that header) . Last meaningful commit on it seems to be made in 2016.