Good morning! I don't think that is possible to do so, but you could suggest that feature to Mozilla at input.mozilla.org.

Hope this helps!

Warm regards, Jeremy West (jeremynwest)

There is a pref available on the about:config page that you can modify to set where to display the scroll bar. Set the layout.scrollbar.side pref to '3' to place the scroll bar at the left side. Set the layout.scrollbar.side pref to '2' to place the scroll bar at the right side. See http://kb.mozillazine.org/layout.scrollbar.side

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox