Not sure if it counts as a course but Joyce Carol Oates's MasterClass on writing short fiction. If you can write short, you can write long. If you can write fiction, you can write anything.
Tap into yourself to find some idea as a core. Just write about it, two minutes. No more than two pages. Look at it from different perspectives. Try different forms.
It was surprising to be able to use it for work to get motivation. Write a monologue from the perspective of a user. Or as a PM. QA. Engineer. Sales. A good monologue goes through an arc of emotions, from frustrated to angry, from anxious to sad, bored to content. Is it empathy? It's motivating, at least.
This is going to sound lame to most of the folks here, but I just finished a college algebra class. I’ve been doing database/software development/IT work for more than a decade but I have virtually no math background besides what I picked up my freshman year of high school.
I recently started working at a university so I’m taking advantage of the tuition reimbursement to build up my math knowledge. It’s a long-term project because I can only take one class a semester, but I’ll probably stay here until retirement (wife is tenure-track faculty at same university), so I’m in no rush.
I have had a long-standing interest in digital signal processing as it relates to music and audio. Any math or physics training that can help me get makes heads of something like ‘The Scientist and Engineer's Guide to Digital Signal Processing’ would be great.
Honestly though, my math-related knowledge is so stunted that I’ll be happy just to gain a sense of what all is out there.
Still going through it but Swifty Stacks: https://www.swiftystack.com/ has been such an eye opening for a hobby iOS engineer like myself. I've enjoyed all the content and coming from a web dev background its a breath of fresh air to see a different development style and how to make things performant / make DevEx easy on yourself and your project.
Economics of Money and Banking: https://www.coursera.org/learn/money-banking
Lectures on the Geometric Anatomy of Theoretical Physics: https://www.youtube.com/playlist?list=PLPH7f_7ZlzxTi6kS4vCmv...
Introduction to Dynamical Systems and Chaos: https://www.complexityexplorer.org/courses/98-introduction-t...
Discrete Optimization: https://www.coursera.org/learn/discrete-optimization