Need to send an alarm acknowledgement over MQTT, is there a way that I can read the status of an alarm to send; or can I look at the canned ack button and send after that has been pressed? I just need something to trigger a write message.

Have a look at the PLC Alarm tag type and let me know if it might provide a solution for you:

https://www.vtscada.com/help/Content/D_Tags/D_PLCAlarm.htm

I looked at the tag type but cannot find a way to associate an MQTT address to the tag. The MQTT client driver does not show up in the drop down.

You would have to connect the driver to your MQTT device driver and then set up the addresses using the custom PLC selection from the PLC type.