Ask HN: Is anyone developping Gmail plugins?

I recently started developping a Gmail plugin for a NGO (to ease the workflow of sending daily mails to show when we need volunteers, then to enroll them in a slot way faster than the manual way it used to be done). It has been a HUGE success for the team that handles that, leading to a lot less hours spent on manually doing repetitive tasks.

On the other hand, the documentation is quite lacking, and there doesn't seem to be much discussions around that (I had very little with Stackoverflow for example).

This got me wondering, I am the only one doing that sort of stuff? I counted 99 plugins on Gmail marketplace, about half being specific to a product rather than general-purpose.

I'm also wondering about transforming that as a side-business: the 2 NGO I have good insight into have hugely inefficient process to fill their opening hours with volunteers, leading to burnout of the team who handles that booking.

As anyone turned that sort of opportunity around Gmail plugins in a business?