Systems Thinking. It helps you understand how components interact to form a system, and how to change it. Books:
- The Goal: https://www.amazon.com/Goal-Process-Ongoing-Improvement/dp/0...
- Thinking in Systems: https://www.amazon.com/Thinking-Systems-Donella-H-Meadows/dp...
Pertinent for 2023, learn about costs. If you're an engineer, understand how much the services you're responsible for are costing. How can you reduce that cost? Can you optimize costs enough to save your monthly salary?