You can put JS functions into a bookmark that will fire on the webpage you are on.
For example:
DELETE ALL IMAGES ON WEBSITE:
javascript:(function(){ [].slice.call(document.querySelectorAll('img, .gist')).forEach(function(elem) { elem.remove(); }); })()
How to use the Bookmarklets:
More recipes here:
https://sites.google.com/view/awesomejavascripthacks/how-to-use