Post Changed Trigger

Hello, all. I’m struggling with the Post Changed Trigger and I can’t seem to find documentation on it. What is the Custom Field Name it is seeking? I want this workflow to run whenever a post is created in a certain category.

I set the Post type to “Post”, Post status to “Published” and Post author to “Any”. I set the Taxonomy to “Category” and the Taxonomy name to the category slug.

I then set Custom field name to {TRIGGER.post_title} equals *. However, this generates this error:
Make sure that you specify the correct list variable or its index: Element of the list is not set or the index is out of range: {TRIGGER.post_title}

I’ve tried several variations:
Make sure that you specify the correct list variable or its index: Element of the list is not set or the index is out of range: {TRIGGER[post_title]}
Make sure that you specify the correct list variable or its index: Element of the list is not set or the index is out of range: {TRIGGER.ID}
Unknown variable, make sure that you specified the correct name: Variable is not set: {$post.post_title}

I even tried * equals * but that did not trigger the workflow.

What are we supposed to use for the Custom field name? Thanks