Firefox Tree Style Tab extension & hide native tabs

1. 地址栏空白处右键Customize Toolbar...，勾选Title bar
2. 安装Tree Style Tab扩展
3. 在地址栏输入about:config搜索toolkit.legacyUserProfileCustomizations.stylesheets改为true
4. 在地址栏输入about:support搜索Profile Directory，Open Directory打开路径
5. 新建chrome文件夹，文件夹下新建userChrome.css，文本输入以下内容保存

/* hides the title bar */
#titlebar {
  visibility: collapse;
}

/* hides the sidebar */
#sidebar-header {
  visibility: collapse !important;
}

5. 重启Firefox

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https://superuser.com/questions/1424478/can-i-hide-native-tabs-at-the-top-of-firefox