Oh that's slick. Was that all through the customize screen, or was any of it via CSS?

Edited to add:

I had to add the following to move the system UI buttons to the same "bar" as the rest of the UI in Firefox:

    /* Adding empty space for buttons */
    #nav-bar {
      margin-right:80px;
    }

    /* For dragging whole window by mouse*/
    #titlebar {
      appearance: none !important;
      height: 7px;
    }

    /*
      Fix for main menu calling by Alt button
      THIS BREAKS THE UI FOR ME!!
      */
    /* #titlebar > #toolbar-menubar {
      margin-top: 10px;
    } */

    /* Move minimize/restore/close buttons to empty space */
    #TabsToolbar > .titlebar-buttonbox-container {
      display: block;
      position: absolute;
      top: 17px;
      right: 1px;
    }

From: https://github.com/piroor/treestyletab/wiki/Code-snippets-fo...