Bring vertical tabs to Firefox + Other useful stuff

Procedure

1. Set up ‘Sideberry’

   1. Install Sideberry from extension store.
   2. Click ‘Cog’ ⚙️ icon in the top right of the sidebar.
   3. Choose ‘Style Editor’ from side menu.

      1. Add these lines to set properties for fonts and background colors;

         #root.root {--tabs-indent: 15px;}
         #root.root {--tabs-activated-bg: #BC8F8F;}
         #root.root {--tabs-font: 0.77rem sans-serif;}
         #root.root {--frame-bg: #f3b1a6;}
         #root.root {--toolbar-el-overlay-active-bg: rgba(255,255,255,0.133);}
         #root.root {--toolbar-bg: #f3b1a6;}
         
         
         
         #root.root {--toolbar-el-overlay-selected-border: #146fd9;}
         

2. Next, in order to hide horizontal(normal) tabs

   1. Enter about:config in the address bar and select “Accept the Risk and Continue.”

   2. Under “Search preference name,” paste the following text: toolkit.legacyUserProfileCustomizations.stylesheets

   3. Tap the toggle button on the right so the preference says “true.”

   4. Enter about:support in the address bar.

   5. Scroll down to the section that says “Profile Folder,” and click the “Open Folder” (“Show in Finder” on macOS) button.

   6. Create a new subfolder called “chrome” within the folder you just opened.

   7. In the new “chrome” folder, create a new file named userChrome.css.

      
      /* ----- For macOS  ----- */
      .tabbrowser-tab {
      visibility: collapse;
      }
      .titlebar-button {
      height: 27px !important;
      }
      #nav-bar {
      margin-top: -30px;
      margin-left: 80px; 
      margin-right: 40px; 
      box-shadow: none !important;
      border-top-left-radius: 5px;
      border-top-right-radius: 5px;
      }
      
      [uidensity="compact"]:root .titlebar-button {
      height: 32px !important;
      }
      [uidensity="compact"]:root #nav-bar {
      margin-top: -32px;
      }
      
      #titlebar-spacer {
      background-color: var(--chrome-secondary-background-color);
      }
      #titlebar-buttonbox-container {
      background-color: var(--chrome-secondary-background-color);
      }
      .titlebar-color {
      }
      
      #main-window[inFullscreen="true"] #sidebar-box,
      #main-window[inFullscreen="true"] #sidebar-box + splitter {
          visibility: collapse;
      }
      
      #sidebar-box #sidebar-header {
      display: none !important;
      }
      

   8. Restart Firefox to take effect.