Contact Tag Trigger
This allows you to cause something to happen when a contact tag is added or removed. It is fairly limited but still useful.
This will trigger either when a contact tag is added or removed in general, or when a specific contact tag is added or removed.
To use the Call Status Trigger, simply go into Automation -> Workflows and click, "Create New Workflow". (1)
Then choose "Contact Created". Afterwards, you can choose the filters or conditions under which the trigger will fire. (2, 3)