Arc-Adjacent Pinned Tabs by Evan Krummel

When closing the last tab that isn't pinned, this extension opens a new blank tab. This somewhat mimics the behavior of Arc Browser. Works Best with "New Windows" and "New Tabs" set to "Blank Page".

I've also added some basic pinned tab functionality that allows you to return to the original "core" URL using Shift + Cmd + R, right clicking and selecting from the menu, or automatically after 3 hours. I've done my best to make this restart-proof, but we'll see....