The following link shows that there is an ability to create exclusions within audiences, but my instance of Target doesn't seem to have the ability to add an exclusion
Does anyone else have trouble making an exclusion rule with audiences for Target?
Adding a exclusion rule in an Audience is a feature that is available to all the Adobe Target standard Users. Can you please share your Adobe Target account details i.e. Company Name & the Audience Name in a private message so that we can debug the issue at our end ?