https://support.mozilla.org/en-US/questions/1232532#answer-1150609

this question was answered before but not show real solution, and i cannot tap to I save same problem

Any special reason why you use this old Firefox 73.0.1 version and not the current release (82.0.2) ?

There should be a 'show sidebar' toolbar button available on the customize page that you can add to the Navigation Toolbar.

Try the Firefox version from the official Mozilla server if you currently use a version from the repositories of your Linux distribution.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release