Civimobile API 4.0 QR code question
This option is not related to CiviMobile. Rather becomes available once you install QR code check in extension https://github.com/progressivetech/net.ourpowerbase.qrcodecheckin

And yes, you are reading it correctly, only a single qr can be available at a time. This is limitation of this extension, unless someone codes it in a different way. But please see a discussion why it can’t be done with existing extension 
https://github.com/progressivetech/net.ourpowerbase.qrcodecheckin/issues/6