Josiah Smith

I know triggers only work for Created tickets, and Updated tickets. 

Is there a way to:
IF ticket is OPEN 
Ticket>Comment Text; Contains at least one of following words; “words” 
Add Tag => tag-name
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I've tried setting it to:
ALL
Ticket > Ticket Status; is; Open
ANY
Ticket>Comment Text; Contains at least one of following words; “words” 
ACTIONS
Add Tag => tag-name

But it only scans the newly created tickets for the keywords, rather than the bucket of tickets that I have which is what I want it to do. 

After reading, I'm seeing that Trigger may not be the right tool for this, is there a tool that would enable this to happen?