Is it possible to put a little icon on the recordings that have been “watched”. A little green icon like the web UI for recordings would be good.
Do you mean in the DVR's web UI, or a client app?
In the client apps, watched (or partially watched) programs/movies have a green progress indicator across the bottom of the thumbnail. Watched or in-progress recordings will have a green indicator; unwatched videos will not have any indicator present. (On the Recordings page, the thumbnail indicator is replaced with the green circle beside the recording, filled in according to the progress viewed.)
On the Movies the watched green line goes away after a while (fully watched) and there is no way to know you watched it unless you select the movie,
I see it now if you select the Library then Movies you see the green bar ... but if you go directly to Movies section it is not there. Not really useful as the library Section only shows 11 movies ... more does not have indicators.