After adafruit/circuitpython#4868 was closed I tried again a hid_descriptor with multiple report id's for one device.
Using the latest libraries it is clear, that "/lib/adafruit_ble/services/standard/hid.py", line 419 still has the catch for multiple report id's

  if len(reports) > 1:
    raise NotImplementedError(
      "Only one report id per Application collection supported"
  )

Also, it looks to me, that the following code, which adds ReportOut's and ReportIn's is not prepared to handle multiple report id's for one device.

@dhalbert Just commenting out the if statement does not help.

I think, that there are also problems elsewhere, because when using the standard_hid_descriptor with an added braille_hid_descriptor, also a standard keyboard from this descriptor is not working anymore.

Here is a "minimal" sample file:
code.zip