Here is my flow:
[{"id":"97c89a5e.34694","type":"inject","z":"b4370c04.a6c7d","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":260,"y":1520,"wires":[["67700f80.1bdd"]]},{"id":"67700f80.1bdd","type":"template","z":"b4370c04.a6c7d","name":"","field":"payload","fieldType":"msg","format":"handlebars","syntax":"mustache","template":"product,takt\nball,20\ntrain,30\nhat,60","output":"str","x":360,"y":1580,"wires":[["c0e5b5dc.9fe7b"]]},{"id":"c0e5b5dc.9fe7b","type":"csv","z":"b4370c04.a6c7d","name":"","sep":",","hdrin":true,"hdrout":"none","multi":"mult","ret":"\\n","temp":"","skip":"0","strings":true,"include_empty_strings":"","include_null_values":"","x":400,"y":1640,"wires":[["63d7a04d.fd528"]]},{"id":"63d7a04d.fd528","type":"change","z":"b4370c04.a6c7d","name":"","rules":[{"t":"set","p":"options","pt":"msg","to":"payload.{product: $}","tot":"jsonata"},{"t":"delete","p":"payload","pt":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":590,"y":1640,"wires":[["b72e9cd3.3baa58","bc09b5df.ea4a5"]]},{"id":"b72e9cd3.3baa58","type":"ui_dropdown","z":"b4370c04.a6c7d","name":"","label":"test","tooltip":"","place":"Select option","group":"a21aeffd.644dc8","order":4,"width":0,"height":0,"passthru":false,"multiple":false,"options":[{"label":"","value":"","type":"str"}],"payload":"","topic":"topic","x":800,"y":1640,"wires":[["bc09b5df.ea4a5"]]},{"id":"bc09b5df.ea4a5","type":"debug","z":"b4370c04.a6c7d","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":750,"y":1560,"wires":[]},{"id":"a21aeffd.644dc8","type":"ui_group","name":"Group 2","tab":"80b00f09.0a7c7","order":2,"disp":true,"width":6},{"id":"80b00f09.0a7c7","type":"ui_tab","z":"","name":"Products","icon":"dashboard","order":4,"disabled":false,"hidden":false}]
When I select "ball" in the dashboard. Nothing comes out.
Edit: This is the original flow I got from you, the only thing I changed is: payload.{product: $}
As you described in post 4