I created my own low-level discovery rule - "drbd.connected.discovery" which returning drbd devices based on some conditions.

zabbix_get -s test -k drbd.connected.discovery
{"drbd.connected.discovery":[{"

{#DRBD-CONNECTED}":"drbd6"},{"{#DRBD-CONNECTED}

":"drbd7"},{"

{#DRBD-CONNECTED}":"drbd8"},{"{#DRBD-CONNECTED}

":"drbd10"},{"

{#DRBD-CONNECTED}":"drbd12"},{"{#DRBD-CONNECTED}

":"drbd13"},{"

{#DRBD-CONNECTED}":"drbd14"}]}

JSON format seems ok.

Empty host "test" (no items) linked to the template with this discovery rule (the only one) returning:

Cannot create item [drbd.connected.status[{#DRBD-CONNECTED}

]]: item already exists