Concord 4 - group 34 sensor group event trigger

I have a GE Concord 4 with currently one wireless carbon monoxide detector. I plan on adding more carbon monoxide detectors in the future. I have a need for an output to activate when a co detector trips. Gas sensors are sensor group 34, however, of all the sensor group event triggers, 34 is not one of them. I currently have the output programmed to the sensor number of the one detector. I could program the output to “any auxiliary alarm” but I find it sloppy. Is there any other sensor group I could put the sensor on just so I could use its trigger (besides HOM groups, already using all of them) or is there a secret trigger number I can use that will trip for group 34? Perhaps I could use sensor group 23, but I’d prefer to keep carbon monoxide under sensor group 34.