It would be useful if Firefox recorded which configs the user changed. Imagine if you could view a chronological, tabular list of all configs that you changed. Name, default value, changed value, date.
Firefox has all of this except the date. `about:config` lists all config values, values in bold do not match their default or do not exist by default, values can be reverted with one click, and there's a checkbox to filter out unmodified items.
But does that include the personalized settings for a specific site?
I mean Tools menu -> Page Info -> Permissions
An example: the gong doesn't sounds when a game starts in lichess if you have autoplay disabled for sound. You need to allow that for the site. There are other configurations there like accepting cookies, etc.
about:preferences#privacy, scroll down a bit, it's under "Permissions". You can also adjust it when on the site, using the icon at the left of the URL bar.