terminal – The right way to learn a nested key with ‘defaults’

I can learn preferences from a website, and I can learn a single key deep, for instance:

defaults learn com.apple.Terminal "Window Settings"

Nevertheless, I can’t dereference a key deeper than depth=1 with the defaults command. For instance, I wish to learn the Primary beneath Window Settings. I might count on to have the ability to do one thing like this:

defaults learn com.apple.Terminal "Window Settings" Primary

It seems like defaults solely works with a set depth:

The area/default pair of (com.apple.Terminal, Primary) doesn't exist

However certainly I can use it to govern dictionaries? What utilities can be found?