1 - Visit about:config Search for toolkit.legacyUserProfileCustomizations.stylesheets, set it to true While you're here, you can enable other customizations you may want here.
2 - Visit about:support In the Profile Directory row, copy the full path May look something like: /home/{username}/.mozilla/firefox/...
3 - If there is no chrome" folder, create one.
4 - Then, inside the chrome folder, create a file called "userChrome.css", Copy & Paste the contents of userChrome.css into the file.
5 - Install Sidebery https://addons.mozilla.org/en-US/firefox/addon/sidebery/
6 - Add This style to Sidebery Styles Editor.
#root.root {--tabs-progress-bg: #ffffffff;} #root.root {--tabs-activated-fg: #000000ff;} #root.root {--tabs-activated-bg: #efefefff;} #root.root {--general-margin: 4px;} .NavigationBar { display: none; }
7 - Make sure to Customise toolbar, Add/Remove Spaces.
8 - If you have any issues with Close/Minimize Buttons on windows or Mac try to alter these CSS properties in "min-one-line/userChrome.css" file.
.titlebar-buttonbox-container { display: block !important; position: absolute !important; top: 13px; left: 4px; }