Hi Chiu,
I created a dummy zone on Partition 1 and also did a full system write rather than selective and now both the Set/Unset Status Output and Siren Output on Partition 0 are working.
The use case is twofold - 1. controlling the siren from Samsung Smartthings and also from Amazon Alexa via a Smartthings skill. And vice versa - so that Comfort siren trigger also triggers Smartthings managed alerts - push notifications, sirens etc. 2. controlling Arm/Disarm from Smartthings to Comfort and vice versa.
I\'ve now achieved both using two Shelly 1 relays (£17 each) which are dry contact, remote (zigbee, zwave, wifi, MQTT etc) and also externally switched 12v relays. The dry contact relay is attached to an input zone for each relay, one for Siren/Strobe, one for Arm.
On remote triggering of each relay, the corresponding input zone is triggered with a response to trigger on or off the siren and arm or disarm Comfort, separately. I\'m using four simple responses, two for each relay, and a flag for the Siren status to also reflect in a simple \'Siren\' toggle switch in the Comfort ios app. The difficulty I was having was reflecting the Siren and Arm status from Comfort to Smartthings triggered via an Output zone to the external input switch on each relay. Hence the desired use of the Status Output and Siren Output events. That is all now working perfectly.
I realise there are multiple other ways to do this, but this appears to be the simplest and most straightforward and lowest cost, as a catch all for all siren and arm events. From a Smartthings perspective we are only interested in triggering Away mode remotely on Smartthings security set and of course being able to then set security off via the Comfort keypad and hence then also disarm security in Smartthings.
This basically allows for a hybrid but somewhat synchronised system of older comfort controlled security and newer Smartthings compatible components and control. With a much louder and more resilient Comfort controlled siren than the feeble Arlo doorcam alarm in play

. It\'s not perfect, can\'t (currently) tell specific zone triggers in Smartthings, but incredibly useful nonetheless. You could of course go further with relays on each zone though. Indeed this method of hybrid control will work with any Smarthub as the Shelly Switches are pretty much universally standards based.
Thanks again for your helpMike