General idea is as follows. To import this flow copy the code, the whole thing. Then go to your NR instance, click on the three lines in the top right corner and then click import. Paste this code there and click import again.
[{"id":"0952e6fe030cc582","type":"server-state-changed","z":"878e74c2.7f39c8","name":"CO2","server":"9405c3fe.d0a6c","version":4,"exposeToHomeAssistant":false,"haConfig":[{"property":"name","value":""},{"property":"icon","value":""}],"entityidfilter":"sensor.co2","entityidfiltertype":"exact","outputinitially":false,"state_type":"num","haltifstate":"","halt_if_type":"str","halt_if_compare":"is","outputs":1,"output_only_on_state_change":true,"for":"0","forType":"num","forUnits":"minutes","ignorePrevStateNull":true,"ignorePrevStateUnknown":true,"ignorePrevStateUnavailable":true,"ignoreCurrentStateUnknown":true,"ignoreCurrentStateUnavailable":true,"outputProperties":[{"property":"payload","propertyType":"msg","value":"","valueType":"entityState"}],"x":270,"y":1920,"wires":[["d09aed3a81e7066e"]]},{"id":"d09aed3a81e7066e","type":"switch","z":"878e74c2.7f39c8","name":"","property":"payload","propertyType":"msg","rules":[{"t":"lt","v":"800","vt":"num"},{"t":"btwn","v":"801","vt":"num","v2":"1000","v2t":"num"}],"checkall":"true","repair":false,"outputs":2,"x":410,"y":1920,"wires":[["04d63c32ae620382"],["4cba15f44812163c"]]},{"id":"04d63c32ae620382","type":"api-call-service","z":"878e74c2.7f39c8","name":"fan_mode 20%","server":"9405c3fe.d0a6c","version":5,"debugenabled":false,"domain":"","service":"","areaId":[],"deviceId":[],"entityId":[],"data":"","dataType":"jsonata","mergeContext":"","mustacheAltTags":false,"outputProperties":[],"queue":"none","x":620,"y":1880,"wires":[[]]},{"id":"4cba15f44812163c","type":"api-call-service","z":"878e74c2.7f39c8","name":"fan_mode 40%","server":"9405c3fe.d0a6c","version":5,"debugenabled":false,"domain":"","service":"","areaId":[],"deviceId":[],"entityId":[],"data":"","dataType":"jsonata","mergeContext":"","mustacheAltTags":false,"outputProperties":[],"queue":"none","x":620,"y":1920,"wires":[[]]},{"id":"9405c3fe.d0a6c","type":"server","name":"Home Assistant","version":5,"addon":true,"rejectUnauthorizedCerts":true,"ha_boolean":"y|yes|true|on|home|open","connectionDelay":true,"cacheJson":true,"heartbeat":false,"heartbeatInterval":30,"areaSelector":"friendlyName","deviceSelector":"friendlyName","entitySelector":"friendlyName","statusSeparator":"at: ","statusYear":"hidden","statusMonth":"short","statusDay":"numeric","statusHourCycle":"h23","statusTimeFormat":"h:m","enableGlobalContextStore":true}]
I assume you’ve only manipulated your entity through the UI, never used code, and without the code I don’t know how to set the fan_mode in NR.
What device is that entity? what integration did you use to integrate this device?