I feel your pain! Not easy, but doable. Can get complicated when a user does many modifications via userChrome.css. And IMO too many people are using if far more than was conceived of when Netscape came up with that 'optional user file' that can be added the minor tweaks - part of Firefox which is derived from the original mid-1990's Netscape Navigator. https://www.reddit.com/r/firefox/comments/7dvtw0/guide_how_to_edit_your_context_menu/ <br> Here's the Firefox source code to see the contextual menu items: <br> https://searchfox.org/mozilla-release/source/browser/base/content/browser-context.inc This is where you can get the scripts for userChrome.css .<br> https://github.com/stonecrusher/simpleMenuWizard <br> Updates provided there as needed, when Firefox is changed. Current version v1.26 is 4 months old now. There are 16 separate '''CSS''' files that can be used to deal with the various Contextual Menus, one at a time to "toggle off" each menu item by setting that pref. <br> My advice is to use the '''@import url''' feature in the main '''''userChrome.css''''' file and have separate *.css file ''(like for select-context.css)'' saved in the userChrome.css (main file). <br> https://www.userchrome.org/adding-style-recipes-userchrome-css.html I recommend using that '''@import url''' feature to help you troubleshoot future issues that will develop so that each batch of "contextual menu code" can be easily disabled more easily. ''I am still trying to fix what got broke 4 months ago with a Firefox update.''

Thank you very much !