What are some MUST short term training courses that a mid level HR Manager should undertake?

I have been teaching these basic courses both internally and as a consultant for the past 10+ years with positive feedback on the relevancy of the topics.

Interviewing and Hiring - Everything from how to create a job description to making a hiring decision to properly onboarding and training new hires.

Management - Transitioning from an individual contributor to working through others

Delegation - How to move your workload onto others so that you are managing vs doing

Motivation - How to get others to work for you at their peak capacity

Communication - How, What and Why to communicate to your employees

Coaching/Feedback - How to get your employees to improve their work and grow by providing meaningful insights and suggestions

Some Personality Assessment - I prefer to use MBTI. I use this to help managers gain insight into their work style and other preferences.

These should definitely be enough to get managers started in the right direction.