[ST Edge] How to update/increase the number of endpoints?

You are right. I always thought deviceId were part of the fingerprint.
But now I think the deviceId defined there is for the main endpoint.

I found this post: [ST Edge] DeviceId and Zigbee profileId in Edge driver's fingerprint - #2 by nayelyz

zigbeeGeneric:
  - id: "dimmer-generic"
    deviceLabel: "Zigbee Dimmer"
    zigbeeProfiles: 
      - 0x0104 # HA or
      - 0xC05E #ZLL
    deviceIdentifiers: 
      - 0x0101 # Dimmable light
    clusters: 
      server: 
        - 0x0006 # on/off cluster
        - 0x0008 # level control cluster
      client:
        - 0x0019 # outCluster if needed
    deviceProfileName: on-off-level-bulb

So deviceId follows a pattern.

PS.: deviceId is an excellent subject for a new thread.