Firefox without a VIM-ish extension is so awkward anymore. I wish this could work to all pages (e.g., FF'S own Add-ons page, error pages, etc.) but I believe that's a just a limitation of WebExtensions (for the sake of security). My habits will just have to learn to adapt.

I'm using this with the Textern add-on so that I can use gvim to edit text areas. They are happily working together.

I prefer the simplicity of the configuration as JSON, though would perhaps prefer it to be external so that I could keep it under Git. For such a young new add-on, it's off to a great start!