Switch on by publishing a command and a json string

Setup, Configuration and Use Beginners
2

Firstly, you have a typo:

I’m on phone, so can’t provide a complete solution, but for this I would probably use the formatBeforePublish option for your Channel

That would make your Channel something like:

stateTopic="stat/ZBBridge/RESULT",
commandTopic="cmnd/ZBBridge/ZbSend",
formatBeforePublish="{\"device\":\"Plug1\",\"send\":{\"Power\":%s}}"
on="On",
off="Off"