I don't us the rfKey method at all as it's limited to 16, that's just 8 devices (ON/OFF)
I just watch the console when pressing the remote buttons and note the values of rfSync, rfLow, rfHigh and rfcode then inject an array containing these values into a series of change nodes connected to a MQTT out node. Works a treat. Have a look at the flow below:
[{"id":"1f74cd3c.990323","type":"mqtt out","z":"5542a8a0.2ca958","name":"","topic":"","qos":"","retain":"","broker":"33b374f4.96a50c","x":790,"y":460,"wires":[]},{"id":"7a82df4b.03e23","type":"inject","z":"5542a8a0.2ca958","name":"On","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"num","x":90,"y":500,"wires":[["85828f1b.1d25e"]]},{"id":"96bcea02.0e7f28","type":"change","z":"5542a8a0.2ca958","name":"rfSync","rules":[{"t":"set","p":"payload","pt":"msg","to":"rfcmnd[0]","tot":"msg"},{"t":"set","p":"topic","pt":"msg","to":"cmnd/rfbridge1/rfSync","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":550,"y":420,"wires":[["4dcd768f.3462e8","1f74cd3c.990323"]]},{"id":"4dcd768f.3462e8","type":"change","z":"5542a8a0.2ca958","name":"rfLow","rules":[{"t":"set","p":"payload","pt":"msg","to":"rfcmnd[1]","tot":"msg"},{"t":"set","p":"topic","pt":"msg","to":"cmnd/rfbridge1/rfLow","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":550,"y":460,"wires":[["a90310e5.3cc07","1f74cd3c.990323"]]},{"id":"a90310e5.3cc07","type":"change","z":"5542a8a0.2ca958","name":"rfHigh","rules":[{"t":"set","p":"payload","pt":"msg","to":"rfcmnd[2]","tot":"msg"},{"t":"set","p":"topic","pt":"msg","to":"cmnd/rfbridge1/rfHigh","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":550,"y":500,"wires":[["e61e8605.bb05b8","1f74cd3c.990323"]]},{"id":"e61e8605.bb05b8","type":"change","z":"5542a8a0.2ca958","name":"rfcode","rules":[{"t":"set","p":"payload","pt":"msg","to":"rfcmnd[3]","tot":"msg"},{"t":"set","p":"topic","pt":"msg","to":"cmnd/rfbridge1/rfcode","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":550,"y":540,"wires":[["1f74cd3c.990323"]]},{"id":"85828f1b.1d25e","type":"change","z":"5542a8a0.2ca958","name":"Dishwasher ON ","rules":[{"t":"set","p":"rfcmnd","pt":"msg","to":"[5380,170,530,\"#155533\"]","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":320,"y":500,"wires":[["96bcea02.0e7f28"]]},{"id":"d311681e.acd6b8","type":"change","z":"5542a8a0.2ca958","name":"Dishwasher OFF","rules":[{"t":"set","p":"rfcmnd","pt":"msg","to":"[5350,180,530,\"#15553C\"]","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":330,"y":540,"wires":[["96bcea02.0e7f28"]]},{"id":"56bb2280.88bd7c","type":"inject","z":"5542a8a0.2ca958","name":"Off","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"num","x":90,"y":540,"wires":[["d311681e.acd6b8"]]},{"id":"a6452426.d99e28","type":"link in","z":"5542a8a0.2ca958","name":"dwo","links":["7af67686.7051a8"],"x":195,"y":480,"wires":[["85828f1b.1d25e"]]},{"id":"ac5dcd52.90357","type":"link in","z":"5542a8a0.2ca958","name":"dwoff","links":["120e5a59.698036"],"x":195,"y":520,"wires":[["d311681e.acd6b8"]]},{"id":"ce789c2c.5febc","type":"inject","z":"5542a8a0.2ca958","name":"On","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"num","x":90,"y":400,"wires":[["d5ba286f.4b3a68"]]},{"id":"d5ba286f.4b3a68","type":"change","z":"5542a8a0.2ca958","name":"Tumbledryer ON ","rules":[{"t":"set","p":"rfcmnd","pt":"msg","to":"[5380,170,530,\"#1555C3\"]","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":320,"y":400,"wires":[["96bcea02.0e7f28"]]},{"id":"8e3dd12c.7093a","type":"change","z":"5542a8a0.2ca958","name":"Tumbledryer OFF","rules":[{"t":"set","p":"rfcmnd","pt":"msg","to":"[5350,180,530,\"#1555CC\"]","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":330,"y":440,"wires":[["96bcea02.0e7f28"]]},{"id":"f7121559.3471d8","type":"inject","z":"5542a8a0.2ca958","name":"Off","repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"num","x":90,"y":440,"wires":[["8e3dd12c.7093a"]]},{"id":"fdd5a509.f6e5f8","type":"link in","z":"5542a8a0.2ca958","name":"tdon","links":["21592798.5624a8"],"x":195,"y":380,"wires":[["d5ba286f.4b3a68"]]},{"id":"443e9e9e.ae188","type":"link in","z":"5542a8a0.2ca958","name":"tdoff","links":["5d9ff029.92c2e"],"x":195,"y":420,"wires":[["8e3dd12c.7093a"]]},{"id":"33b374f4.96a50c","type":"mqtt-broker","z":"","name":"","broker":"192.168.1.2","port":"1883","clientid":"","usetls":false,"compatmode":true,"keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","closeTopic":"","closePayload":"","willTopic":"","willQos":"0","willPayload":""}]
[edit] ignore the link nodes!!