Many of you know UserScripts (GreaseMonkey and forks). Less known is, that much of the function can be achieved without an extension, but only 2 little script files in the Firefox program folder. The modification is called "userChromeJS": https://github.com/Endor8/userChrome.js ... userChrome
I use several userscripts, for example to switch on/off SVG, Javascript, Pictures and CSS with buttons.
But some things in scripts are a too difficult for me and I have questions. Are people here interested in this?