YouTube TV has rolled out custom multiview for subscribers. This has long been a key selling point for sports, but now the feature will work across all channels. Subscribers can even mix-and-match across packages, which includes stuff like NFL Sunday Ticket. That means users can set up their own fully customizable screens that display whatever they want, from football games to the weather and that latest episode of a CBS procedural. The company began testing this a few years back , so we've been waiting a while for a true multiview option on the platform that stretched beyond sports. It's all accessed via a tool called the "multiview builder" which is exactly what it sounds like. There are some minor caveats here. The multiview feature is currently only for live content, so there's no way to, say, watch a basketball game and an episode of Daredevil: Born Again at the same time. Also, YouTube says some devices won't support custom multiview.…