Thank you 
You are right, that works using the dotted syntax 
But unfortunately comparing 2 nested keys does not work:
[{"id":"c8272a46.29f618","type":"tab","label":"Flow 7","disabled":false,"info":""},{"id":"e9e3df88.d999a","type":"switch","z":"c8272a46.29f618","name":"","property":"payload.test2","propertyType":"msg","rules":[{"t":"eq","v":"12345","vt":"str"},{"t":"eq","v":"payload.test4","vt":"msg"}],"checkall":"true","repair":false,"outputs":2,"x":430,"y":280,"wires":[["bbc36929.65d278"],["d52d4950.e7bcf8"]]},{"id":"c6b06bcf.226d48","type":"inject","z":"c8272a46.29f618","name":"test","props":[{"p":"topic","vt":"str"},{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"dd","payload":"{\"test\":\"2\",\"test3\":\"2\",\"test2\":{\"xx\":\"12345\"},\"test4\":{\"xx\":\"12345\"},\"payload\":\"...\"}","payloadType":"json","x":380,"y":160,"wires":[["e9e3df88.d999a"]]},{"id":"bbc36929.65d278","type":"debug","z":"c8272a46.29f618","name":"case1","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":600,"y":240,"wires":[]},{"id":"d52d4950.e7bcf8","type":"debug","z":"c8272a46.29f618","name":"case2","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":590,"y":340,"wires":[]}]