A bookmarklet that spawns a little box that runs whatever you type as JS
javascript:var%20d=document;var%20s=d.createElement('script');s.src='https://grosserly.github.io/js-inject/inject.js';d.body.appendChild(s);void(0);
javascript:var d=document;var s=d.createElement('script');s.src='https://grosserly.github.io/js-inject/inject.js';d.body.appendChild(s);void(0);
I know you can just do this with Inspect Element but Inspect Element's disabled on some of the things I use
Thanks to Alex Leone, David Nufer, and David Truong; the people behind Katamari Hack; whose code I used for reference at times