What controls the 12v circuit to each cabinet? Additionally, is it 12v DC or 12v AC? A lot of low voltage circuits around the home are 12v AC. Landscape lighting is a prime example.
Is there a wall switch that turns the cabinets on/off? If so, does it control a power supply for those cabinets, or is the switch itself between the power supply and the lights?
We run our under cabinets at 100% brightness most of the time. They fade up, and fade off when activated by motion, or when turning them on/off. The fade is controlled by the line voltage GE Z-Wave dimmer in the wall which in turn controls the power brick in the cabinet. We get such a warm, even light that others have commented on our under cabinet lighting. They are shocked when I show it to them and tell them I DIYed it. I’ve even been asked to install the same setup sans the z-wave in other homes.
If you have two locations that are isolated from each other that you want to control together, you have a couple of options. If you choose to duplicate what I’ve done, you will either need to run a low voltage wire through the attic/crawlspace/wall to the other location to run off the same circuit. Or, you will need to duplicate the entire setup in both locations and sync them.
The third option to consider is running just a low voltage LED controller. Something like the H801 in each location and sync them together in a smartapp. This is the cheapest option, but you lose physical control of the lights.