I used to just have cookie.txt, this would save in the home folder, as it is taken a relative path. You couild also use the absolute path from root.
I do not set a file path any longer, or auto init and use the init node and save the resulting cookie to a flow context and load the cookie from flow context cookie in the inject.
e.g.
[{"id":"e63c03b3.745b48","type":"inject","z":"d629013b.18a518","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"86400","crontab":"","once":true,"onceDelay":0.1,"topic":"","payload":"alexa","payloadType":"flow","x":100,"y":1460,"wires":[["89e02d64.da77c8"]]},{"id":"89e02d64.da77c8","type":"alexa-remote-init","z":"d629013b.18a518","name":"","account":"c8738129.d902c","option":"initialise","x":290,"y":1460,"wires":[["fc0183e2.5e7c2"]]},{"id":"fc0183e2.5e7c2","type":"change","z":"d629013b.18a518","name":"","rules":[{"t":"set","p":"alexa","pt":"flow","to":"payload","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":490,"y":1460,"wires":[["421c02e9.68fdec"]]},{"id":"c8738129.d902c","type":"alexa-remote-account","name":"alexa remote 2","authMethod":"proxy","proxyOwnIp":"localhost","proxyPort":"3456","cookieFile":"","refreshInterval":"14","alexaServiceHost":"layla.amazon.co.uk","amazonPage":"amazon.co.uk","acceptLanguage":"en-GB","userAgent":"","useWsMqtt":"on","autoInit":"off"}]
