How to change the Output Voltage and Frequency via NodeRed?

I’m trying to change the Ac Output Voltage and frequency. My three MultiPlus II are connected to a DC power source and Modbus/TCP is activated. I’m using the node-red-contrib-modbus nodes, but I just can’t find the right setting. My Cerbo GX wont show me the device list anymore, so finding the correct Unit ID is a bit tricky. Currently I’ve set it to 100.
I’m using a standart inject node with msg.payload and a number, which is injecting into a Modbus write node with FC 6. I always get error codes in the remote console, but never a change in the AC Output. On top of that I’ve tried what feels like every address which could be for AC out.

There were a few people on the old cummunity page that told me it is possible. But no one told me how…
I’m thankful for every tip.