Custom profiles - Fallback for unlisted settings?

[tisimst 1]

Hopefully a simple question, but after spending a bunch of time customizing my profile, I'd like to know how I can track my changes better.

 

So, let's say I start with a profile that comes built-in. Now, I want to make a modification to something, say the wall thickness, so that it changes from 2 walls to 3 walls. I then save it as a new custom profile.

 

When I export my custom profile and look at the contents in a text editor, it doesn't show ALL the settings, but a fairly small subset. How does Cura decide what to do with the other parameters that aren't listed? Does it fall back to the built-in one? Any advice here is helpful.