solved it myself!
solution was:
stil use ifttt webhook post type json
convert the ifttt data with a json node after the http in node
[{"id":"612f3ecd.84333","type":"tab","label":"uservariable with json format","disabled":false,"info":""},{"id":"ca7a476f.2487f8","type":"mqtt out","z":"612f3ecd.84333","name":"","topic":"domoticz/in","qos":"","retain":"","broker":"21fd69bf.668b46","x":982,"y":281,"wires":[]},{"id":"3a92b3cd.9606ec","type":"debug","z":"612f3ecd.84333","name":"debug","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":962,"y":201,"wires":[]},{"id":"2d6074a9.a954ac","type":"inject","z":"612f3ecd.84333","name":"nr1_payload_on","topic":"","payload":"[{\"obj\":\"lantaarn\",\"act\":\"On\"},{\"obj\":\"Lamp tv links\",\"act\":\"On\"}]","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":260,"y":340,"wires":[["4310dae3.f33594"]],"info":"[{\"obj\":\"lantaarn\",\"act\":\"On\"}]\n\n\n"},{"id":"4310dae3.f33594","type":"function","z":"612f3ecd.84333","name":"create the message","func":"msg.payload = { \"value\" : msg.payload};\nmsg.payload.command = \"setuservariable\";\nmsg.payload.idx = 13;\n\nreturn msg;","outputs":1,"noerr":0,"x":622,"y":201,"wires":[["3a92b3cd.9606ec","ca7a476f.2487f8"]]},{"id":"fdc99a96.3d24b8","type":"http in","z":"612f3ecd.84333","name":"LIVE met post json structure uservar","url":"/pvkvar2","method":"post","upload":false,"swaggerDoc":"","x":222,"y":201,"wires":[["4f2cc13e.b38a4","dff4288b.f60918"]]},{"id":"4f2cc13e.b38a4","type":"http response","z":"612f3ecd.84333","name":"responce post","statusCode":"","headers":{},"x":630,"y":80,"wires":[]},{"id":"ab894ebd.31e32","type":"inject","z":"612f3ecd.84333","name":"nr2_payload_off","topic":"","payload":"[{\"obj\":\"lantaarn\",\"act\":\"Off\"},{\"obj\":\"Lamp tv links\",\"act\":\"Off\"}]","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":260,"y":400,"wires":[["4310dae3.f33594"]]},{"id":"8991a61d.3e3a18","type":"inject","z":"612f3ecd.84333","name":"schakelgroep sfeerverlichting aan","topic":"","payload":"[{\"obj\":\"Schakelgroepen\",\"lbl\":120}]","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":310,"y":460,"wires":[["4310dae3.f33594"]]},{"id":"dff4288b.f60918","type":"json","z":"612f3ecd.84333","name":"","property":"payload","action":"","pretty":false,"x":390,"y":100,"wires":[["4310dae3.f33594"]]},{"id":"21fd69bf.668b46","type":"mqtt-broker","z":"","name":"mqttdomoticz","broker":"localhost","port":"1883","clientid":"","usetls":false,"compatmode":true,"keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","closeTopic":"","closeQos":"0","closePayload":"","willTopic":"","willQos":"0","willPayload":""}]