I used standard Emacs extension-points to extend org-mode
Recently I read this beginners guide to extend Emacs. The guide is perfect for starting out with elisp and it shows a lot of care in teaching how to interact with Emacs. To me, the most important bit though is this one, from the section aptly named Emacs Wants You to Extend It. I haven’t written plugins for other editors extensively, but I can tell you this: emacs doesn’t just make deep customization available, but it actively encourages you to make an absolute customization messes masterpiece