You can change the field Blacklisted using a standard "Data Value Change" flow step in any campaign you define.
Their really isn't a trigger for blacklist as it really is done when you think it is necessary. Even the marketo documentation on how to remedy a blacklist (see here) directs users to delete or marketing suspend those that as suspect blacklist email addresses. So really this field is extra and for your use as defined, but nothing in the system will, or should, mark a record as blacklisted.
Hope this helps.
We use the blacklist field for competitors and terminated clients to ensure they are not sent any communication. In which case, I use two different triggers:
1. Data Value Changes
new value contains: (domain of competitor)
2. Status is changed to "Termed Customer"
If you have two triggers in the smart list, they are treated with "OR" logic. The flow of the campaign can be to "change data value: blacklist: true".