How To Enable Save and Quit option in Firefox

     First open Firefox and type about:config in the address bar. If you typed it correctly you should see this:

     Then  press the Accept and Countinue button. If you don’t go on your own and start clicking things there is no risk really.
 

     The next thing you need to do is type browser.showQuitWarning on the search bar. You should see something like on the picture below.

     To enable the Save and Quit functionality of the browser it should say true. If you see it saying false like is shown on the picture you need to double click it or use the first symbol on the right side to change it.