As you can see, there's a bar above the tabs in the Mozilla Browser which gives redundant information. It happened when I updated some extensions but I don't know how to remove it.
May 01, 2019 Getting your Firefox tabs back - TechRepublic Jan 29, 2013 Download Firefox — Free Web Browser — Mozilla Download Mozilla Firefox, a free Web browser. Firefox is created by a global non-profit dedicated to putting individuals in control online. Get Firefox for Windows, macOS, Linux, Android and iOS today! How to Sync and Access Open Tabs in Firefox Across Devices
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[Firefox Tip] Restore “Close Tabs to the Right” and “Close Other Tabs” Options in Tab Context Menu. This tutorial will help you in moving "Close Tabs to the Right" and "Close Other Tabs" options from new "Close Multiple Tabs" sub-menu to the main tab context menu in newer versions of Mozilla Firefox web browser. Firefox 78: Close Multiple Tabs options moved to submenu
You can work with multiple tabs at the same time; switch tabs with the help of a mouse click. Another way to switch from one tab to the other is by using the “ctrl + tab” key. Now you can navigate through windows very easily thanks to tabbed browsing in firefox. Step 4 – Opening up a link in a new tab
How to work with groups of tabs in Firefox While we did include a tab manager in our Top 10 best Firefox extensions, there's a whole lot you can do with groups of tabs in Firefox by default, no extension required. [Tip] How to Restart Mozilla Firefox Without Losing Tabs