Which process step in KDD or CRISP-DM includes labeling of the data?
Data Labeling is a very trivial process as you have mentioned.

As far as I know, it falls under Data Understanding(Exploration Analysis). When you don't know anything about data then you do exploratory analysis to understand and derive some insights. If you don't know the target variable then the problem falls under Unsupervised Learning, as you have mentioned in the question that your problem is unsupervised. So, you don't know your Target Variable, you are trying to make new feature/dimension to get some good insight irrespective of the factor whether you derive your Target Variable or any other feature it falls under Data Preparation(any new derived variables), which ever we think are important for our Analysis