Make sure your link in the email is defined as a Landing Page.

Checking the box allows you to add new email addresses to ACS.  Otherwise the landing page requires an encoded email address be passed into the landing page for updating.  

Wrong community.  This is Adobe Campaign Standard community.  You want Adobe Campaign Classic community.

This may not answer your question, but couldn't you do something like this? 

You are correct with what you stated above.  Your only other option is to set it up as a transactional message and use a data collection.  It works great, but we end up doing content updates in the html and not the editor.  Here are a couple of screenshots for an example. Blessings,  John

We have ACS and I can set up brands just fine.  Click the Adobe Campaign logo in top left corner, then Administration.  Select Instance Settings and then Brand Configuration. 

Instead of an export it is probably easier to save it to an Audience.  Then you can Read the audience and reconcile it to a profile and then use it for segmentation or enrichment. 1. Create a query of records and under additional data add the email address you want to send to.2. Reconcile to a profi...

If your using organization make sure you are using the ProfileAndServicesExt endpoint and not the ProfileAndServices endpoint.

My I suggest it maybe easier to send the notification to the creator of the workflow.  You could reconcile to the creator's profile and then send an email requesting the workflow be changed. Otherwise you will need use a query collection of the workflow ids and reconcile to your profile before sendi...

Copy the topology rule and change the command from logWarning to logError.  To copy the topology rule you will need to export it, then change the code, then import it as a new name.