Edit:. I got it working now, I had to apply the changes described here, and I had extracted the utils into the chrome folder instead of into chrome/utils like I was supposed to.

I followed all the instructions but it doesn’t seem to work, I downloaded the following scripts from here https://github.com/xiaoxiaoflood/firefox-scripts:

If you want a button to manage your scripts, including the ability to disable/enable scripts without needing to restart¹ Firefox or Thunderbird, save rebuild_userChrome.uc.js into chrome.