@Heidi951 ,
When I see the airbnb-generated lock codes, they do show up in both the Schlage app and in Apple HomeKit. In homekit, I can enable the users for other locks, but it's really hard to find which guest is which because they all show up as "Unknown Guest" in HomeKit and there's not a way in there to set a period of time for validity, so it's just not worth messing with.
I was able to write some code because I am a software developer and I found an API that acts as a proxy to Schlage and other locks manufacturers as well. It's called seam.io. I let seam have access to my schlage account (because I can't find any way to get access to a Schlage API directly) and use the seam API to maintain my codes.
If you're able to write code and call an API like seam, you could do what I have done. I loop over the codes on my lock that's integrated with airbnb, find the ones that are for my reservations, and create duplicate codes with the same valid periods on my other locks. I also periodically check for updates (because I might update the checkin time for a reservation to allow early checkin) and update times if they are out of sync.
In case you're not able to do something like that, I could make my solution available for other folks if there's interest. I'd have to put some thought in what I'm willing to commit to in getting it shareable and making sure it stays operating and such before taking on such a project.