OpenMetrics: How to use a Label Expression with more than one variable value?

so the unique values of frontend are the instances, right? That's handled by discovery. So, the 1xx, 2xx, 3xx, 4xx, and 5xx are different datapoints under each instance yeah?

Unfortunately, i'm not sure of the syntax given the current documentation, but you should be able to reference the code in the datapoint definition using something like "Label Expression", "frontend=##WILDVALUE##,code=1xx". You'd repeat for each of the 5 values of the code tag. Sorry i can't be more help.