No first-hand experience, no. But I hope my answer can still be helpful.
Go after the problem. Write articles and resources about the issues that your add-on solves. Publish YouTube videos and in-depth written pieces detailing every tiny feature of the add-on, and how it benefits G Docs users.
It's true that almost no one will read every word of your in-depth piece, or watch all 9 minutes of your video, but that's ok. Google will. And whatever small percentage of those resources applies most directly to searchers will be valuable to them.
Then you've gotta promote these resources. Places like Quora and Reddit are a great start. Don't be overly spammy, just hawking your add-on shamelessly. Be genuinely helpful, and provide links to your articles/videos (because THEY are helpful).
Trust that some of the Quora/Reddit users will visit your resources, and some of those visitors will view your add-on. Not all, but some. If you try to go for 'all', you'll drive people away, especially on Reddit.
Answers like this one on Clarity are another great spot. Facebook and LinkedIn groups. Other forums or online communities.
Find niches and verticals that may frequently encounter your problem. Then find groups of people in those niches/verticals. Again, don't spam. But when those people see that you can understand and relate to their problem—and help them solve it—they will gladly risk a click.
Let your videos/articles do the rest of the work moving them down the funnel toward the add-on.
Hope that helps!
By the way, what does the add-on do?? Super curious now.