Recently, I found myself on a website where I had to tick 100+ checkboxes and there was no "Select all" button on the page. Obviously, I couldn't do this manually, so I wrote the following bookmarklet.
javascript:(function(){for(i of document.getElementsByTagName('input')){if(i.type=='checkbox') i.checked=!i.checked;}})()
Save this as a bookmark in your browser and click on it to toggle all checkboxes on the page you are on.
