This and Vivaldi make me think of emacs/lisp machines with how the UI is customizable with the same scripting language applications are written in. Firefox also

This and Vivaldi make me think of emacs/lisp machines with how the UI is customizable with the same scripting language applications are written in. Firefox also has this, to a lesser extent, and I'm not sure about Chrome. I just wish that sort of feature set were available for the actual platform rather than the giant rube-goldberg machine required to get JS to be performant.