I'm trying to populate a custom free text field with the ticket assignee's email but all the placeholders I'm trying do not work. At this point I'd be satisfied with anything pointing me to the assignee.
This same trigger with that same webhook works perfectly when using placeholder {{current_user.email}}. But for this flow it's no good because it will populate the end-user's email instead.

According to this article (https://support.zendesk.com/hc/en-us/articles/4408886858138), since that works, if I substitute current_user with ticket.assignee it should also work. But it doesn't. I have also tested using assignee_email as appears in the API docs (https://developer.zendesk.com/api-reference/ticketing/tickets/tickets/) and several combinations of assignee that I'm just guessing at, but I'm not getting a hit. If anyone knows what will work I'd reeeeeally appreciate it.
The first example is before I added the @ to the field, and the second is after. This is what it looks like:
