What’s the need for this? If you want to know which preference settings were changed from one release version of Firefox to another, you might find Config Export Firefox add-on useful. This add-on once installed, adds a new option ‘Full Config Export’ to context menu of each preference in about:config, which when selected, exports Firefox about:config settings to a CSV file with preference name, value, type and status.
Export Firefox about:config settings to a CSV file with Config Export add-on
This can be useful in future when Mozilla ships another Firefox release, you can then create another CSV file from the new release and compare that with the previous one to check which about:config preference setting changed and which remained the same.
You can download Config Export add-on from here on AMO.