In search of the lost manual
I'm a new 2020 NoBo 19.5 owner.
There is a button on my antenna plate that turns off the Antenna power. Also, I disconnected the TV from the wall outlet (if you have a 12v TV that connects via a cigarette lighter plug to a wall outlet).
In the "breaker box", there are small fuses for the 12v circuits, separate from the 120VAC breaker "switches". If you know which 12v circuits you need to disconnect . . . just remember to use the correct Amp rating fuse when you re-insert the removed fuses in the Spring. Mine came with a layout of the breakers and fuse amperages on the breaker box door.
Here in the high country, it's a long winter and you are correct in obsessing about not draining the battery over the storage period. I don't have 120VAC outlets anywhere near my storage location, so I've purchased a small solar panel and appropriate solar charging controller to connect to my batteries to keep them charged (and prolong their life) during storage.
I don't suggest getting a disconnect switch or manually disconnecting it if you're charging your battery from an onboard charging system or an onboard solar panel charging system. Because if you disconnect your battery at the terminal, it won't charge during storage.
If you do decide to disconnect your battery, it is generally recommended to disconnect the negative terminal which energizes the frame of your trailer (aka "negative ground"). Also, generally, there are fewer physical negative connections to your negative terminal that you'll need to reconnect in the Spring.
Just another NoBo Newbie searching for that NoBo specific owners manual . . . as the dealer's "instructor" probably knew less than I've learned about my new home on road.
This week's adventure is to search for the rumored "Hot Water Tank Bypass Valve" behind the hidden panels deep under the cabinets . . .