Yes - the Bubble.io documentation is pitiful on how to build plugin. 
However this is great - @vini_brito
http://forum.bubble.io/t/new-plugin-making-course-with-all-included-and-no-knowledge-spared-15-july-2021/160156
I discovered Vini’s book/course materials after months of frustrating figuring it out myself. Save yourself months of pain and get this book/course is my recommendation. Good luck!
No I don’t get a kick-back - I just like Vini’s stuff.