Sending modbus bit

[Steve-Mcl]

You will need to read the value, mask the bit on/off and send the full WORD value back

To mask the bits on/off, use a function node. e.g: Node-red-contrib-remote-io, digital output for joining bool to word - #2 by Steve-Mcl

Alternatively, use the buffer-maker and buffer-parser nodes to conver your data to/from BOOLS in the node-red-contrib-buffer-parser package.