Good question and I don’t have an answer! I am not programming or tech savvy and trying to find Chromium and Brave development related information for end-users is a nightmare. Just providing some sources of information that may help.
Providing chromium/chrome links. Brave does have the same information spread throughout the documentation on Brave GitHub, mostly in the Brave-Core repository. I have been unable to locate centralized lists as with chromium. It is probably there, I just don’t know where to look. Brave GitHub structure confuses me (as does chromium but it is a little better) and I don’t understand what I am looking at most the time!
List of default settings and documentation for adding which has other interesting links. If you check out the links you can find other pages with the same or additional information. Well, a lot of it looks like the same information stored in a different context, but I did not do a line-by-line comparison.
from chromium on google git
https://chromium.googlesource.com/chromium/src/+/refs/heads/master/content/public/common/content_features.cc
An example of a chromium project source (same information?)
https://source.chromium.org/chromium/chromium/src/+/main:content/public/common/content_features.cc
Documentation
https://chromium.googlesource.com/chromium/src/+/HEAD/docs/how_to_add_your_feature_flag.md
Open issue requesting default be identified in flags (enabled/disabled).
https://bugs.chromium.org/p/chromium/issues/detail?id=861590
Interesting article explaining flags:
Other interesting (related) documentation
https://source.chromium.org/chromium/chromium/src/+/main:docs/flag_expiry.md
https://source.chromium.org/chromium/chromium/src/+/main:docs/flag_ownership.md
Hope this helps! Take care. 