Fixed #23384 -- Allowed overriding part of a dictionary-type setting

This change is needed for upcoming changes where settings might be
grouped in a parent dictionary.
From the comments:
"Hey, thanks for this! What license do you release the code under?"

"the found on the internet in a blog post and you're free to use it license :) i guess whatever stackoverflow considers it's posts/answers works for me. BSD-ish etc.
i wouldn't mind/would suggest a link in the a source comment to the post for both attribution and so that others can find the source of the algo/code if need be in the future. that's usually what i do anyway."

But I can specifically ask the author, too.