This Business Case gives lots of reasons why your Manager should authorise your request for training! I have written it for the globally recognised Agile Change Agent qualification, but many of the benefits also apply to the Change Management Foundation and Practitioner course.
As the Chief Examiner of the Agile Change Agent qualification, I thought you might find it useful to understand more about this course.
If you want a more general reminder about why qualifications are useful, read about my experiences in building the capability for managing change in lots of organisations. I have been leading this work for over a decade, and I often have to make decisions about how we will develop new abilities, new skills and new understanding. Transforming our organisations is a constant activity, and is the responsibility of everyone, not just those with the job title Change Manager, Business Transformation Manager or Project/Programme Manager.