Unfortunately about:config isn't reliably browsable in that way. Many of them do nothing, for example.

Also some of the settings are more of a silent cry "please stop doing this" because the browser will disregard them a few versions later.

Some settings do not show up until you know the strings and add them, though.

You can grep the source code (or more expeditiously, unpack the omni.ja and grep that) for all occurrences of the functions that retrieve the preferences: https://stackoverflow.com/questions/3796084/about-config-pre...

Figuring out what they do is a different story, but at least that's one way to get a list of all of the possible ones.

> Look in about:config ... it is indeed disturbingly large and the majority of them aren't officially documented either.

It really is an insane situation. What is up with Firefox's stealth anti-privacy and spammy marketing features controlled by hidden, undocumented settings that are set to (violate privacy and spam me) by default?

What's up is that Firefox is not an open source project (the source is open, the project is not) and Mozilla is an advertisement company. The ad slot is the default search engine and you are the product being sold to Google. This is how advertisement companies behave. They don't care about you. They collect all the data they can, legally or not.