Is there a way to edit genres of owned films?
You can create your own genres with the tag feature. Below the movie title, there's "no tag" written in green. You click on it, then you tag the movie with any words you want.
I have just imported 20 odd TV Series such as The Office, Game of Thrones, Scrubs and they are not listed as TV Series.
In the grids, there's "series" written in red, while in the movie page "series" transforms into the number of episodes, still written in red (for example "73 ep." in the case of Game of Thrones). If you click on the number of episodes, you'll get to the episodes list, where you can rate the episodes/seasons that you've seen to remember where you've stopped a series.
Surely this should be the case so that you can separate your movie DB from TV DB?!
There's a filter "movies vs. series". If it's not already displayed, you have to click the button "Add/Remove Filters".