Do you want to specify a particular key name in subflow's environment variables?
That's my guess, so if correct, then:
- use string value for the name of the key,
- use bracket notation to access the key inside the
msg.payload.
[{"id":"b87b90dd.a04a3","type":"tab","label":"Flow 1","disabled":false,"info":""},{"id":"af477576.468718","type":"subflow","name":"Subflow 1","info":"","category":"","in":[{"x":60,"y":80,"wires":[{"id":"471337c2.b35128"}]}],"out":[{"x":340,"y":80,"wires":[{"id":"471337c2.b35128","port":0}]}],"env":[{"name":"msgTopic","type":"str","value":"MBLightTopic"},{"name":"msgValue","type":"str","value":"msg.payload.MBLight"}],"color":"#DDAA99"},{"id":"471337c2.b35128","type":"function","z":"af477576.468718","name":"MBLight","func":"var msgTopic = env.get(\"msgTopic\");\nvar val_Light = msg.payload[env.get(\"msgValue\")]; // <-- How to decleare in Environment Variables\n\nif(msg.topic == msgTopic) { msg.payload = val_Light; return msg; }\nelse { return null; } ","outputs":1,"noerr":0,"x":200,"y":80,"wires":[[]]},{"id":"95fd80d5.94b35","type":"inject","z":"b87b90dd.a04a3","name":"","topic":"MBLightTopic","payload":"{\"MBLight\":12}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":200,"y":220,"wires":[["99115b7.f606ca8"]]},{"id":"99115b7.f606ca8","type":"function","z":"b87b90dd.a04a3","name":"MBLight","func":"var msgTopic = \"MBLightTopic\";\nvar val_MBLight = msg.payload.MBLight;\nif(msg.topic == msgTopic) { msg.payload = val_MBLight; return msg; }\nelse { return null; } \n\n","outputs":1,"noerr":0,"x":440,"y":220,"wires":[["597bbf8a.d54df"]]},{"id":"597bbf8a.d54df","type":"debug","z":"b87b90dd.a04a3","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":640,"y":220,"wires":[]},{"id":"e89a4d70.f904","type":"inject","z":"b87b90dd.a04a3","name":"","topic":"MBLightTopic","payload":"{\"MBLight\":12}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":200,"y":380,"wires":[["a06d5b92.476078"]]},{"id":"8004c464.4ad7d8","type":"debug","z":"b87b90dd.a04a3","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":620,"y":380,"wires":[]},{"id":"a06d5b92.476078","type":"subflow:af477576.468718","z":"b87b90dd.a04a3","name":"","env":[{"name":"msgValue","value":"MBLight","type":"str"}],"x":440,"y":380,"wires":[["8004c464.4ad7d8"]]},{"id":"ef0b979e.d52548","type":"inject","z":"b87b90dd.a04a3","name":"","topic":"CRLightTopic","payload":"{\"CRLight\":15}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":200,"y":180,"wires":[["99115b7.f606ca8"]]},{"id":"4908c60d.935248","type":"inject","z":"b87b90dd.a04a3","name":"","topic":"CRLightTopic","payload":"{\"CRLight\":15}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":200,"y":340,"wires":[["a06d5b92.476078"]]}]
