You are able to defer many devices together in the alarm manager in Iris.

We refer to this as bulk editing the devices.

In the alarm manager, select all the devices that you need to edit and click the bulk edit icon at the top of the alarm manager as indicated here.

Note that you will have to select more than one device to be able to click here.

The bulk edit popup will be displayed.

All the fields that you are not able to edit will be greyed out. The fields that you can edit will be white. 

To defer all the alarms that you have selected, click defer from the drop-down in the Change status field. This will defer all the selected alarms until the state of these alarms changes.

Click Save.

As you can see here, you can also change the status of these alarms as listed in the drop-down. This is great as you don't have to do this for each one individually.