How to find the rules where a device is used
Carlo just brought to my attention an incredibly useful tip. To find where a switch/meter/other device is used in your rules, just drag the device from the "Devices" panel on the right to the "My home rules" panel at the top. This creates a filter which shows only the rules where the device is used. It makes you wonder what other filters we could be using, if we only knew about them.
At this point, please resist the temptation to scream "how did I not know about this 3 years ago?!" and go outside and shoot yourself.