Hit me with stories of extensions/integrations and other "Step 1" businesses. I'll go first

There's a couple episodes on Indiehackers of Chrome extensions or smaller apps you'd find in a marketplace to complement a bigger product. Rob Walling calls them Step One businesses. I recently made my first and I'm looking for inspo for a second or even help on how to find an idea

Here is my contribution:

Closet tools, Chrome Extension automation for Poshmark. A clothes reseller. It makes 38K
https://www.indiehackers.com/podcast/187-jordan-oconnor-of-closet-tools

An MFM podcast mentioning podcasts
https://podcasts.apple.com/ie/podcast/163-plugins-making-millions-gumroads-crazy-valuation/id1469759170?i=1000514198369

I'm certain there was another episode on indiehackers of an accessibility plugin for the browser but I can't find it.