I’ve often wondered why the Firefox Sidebar was placed on the left side of the window. I personally find that it distracts my focus while browsing when placed on the left. This quick-tip will show you how to move it to the right side of the Firefox window.
Switching the Sidebar from one side to the other used to require an add-on, but at some point Mozilla decided it should be a built in feature. Open the Sidebar and click the small ‘down arrow’ (see image below) next to Bookmarks
Choose Move Sidebar to Right from the menu.
Ta-da! Now your Sidebar is on the right side of the screen.
If you decide you did in fact prefer it on the left side of the screen, repeat the above steps but choose Move Sidebar to Left