I have done it! I have published my very first Office Web Add-in to the Microsoft Store. After years and years of blogging about it, I wrote an add-in for something I needed. It is true that necessity is the mother of all invention. 
The add-in is called the Trello Taskpane for Word. It is a simple add-in that connects Word to your Trello boards, so that you can insert information you have collected in Trello into your documents. I do research on the web for various topics and send snippets and pages to Trello cards where I organize and refine them. Then I found myself copy/pasting the information from Trello into Word getting lost on the task switching. Now, I can remain in Word, select the cards I want, and insert them without ever leaving Word. How’s that!
It was also a fun exercise for me to combine the two types of extensions I have found to enjoy writing (Office and Trello). More importantly, it is a useful tool that I think might benefit other writers that use Trello, or writers looking for a new way to keep their notecards and thoughts in a more digital, accessible from anywhere type of format.
Have fun and let me know what you think!