I’ve been steadily going through the WordPress: Plugin Development training course by Jeff Starr on LinkedIn Learning. I’m really impressed with the quality of instruction in this entire set of videos. I’ve learned a lot and it’s really helped me fully understand how to plan, design, develop, and publish a complete WordPress plugin. If you’ve wanted to dig down deep in the subject, I’d recommend taking a look. There are a couple free introductory videos, as well as a course outline, that will give you a good idea of what the course is all about.