MacOS - Where is Terminal themes/profiles utilized by Terminal.app on disk?
The properties of themes and profiles are stored in ~/Library/Preferences/com.apple.Terminal.plist in the key Windows Settings/[Name of the Profile]:



Obviously only diffs to a hidden default profile (it's not the Basic profile!) are stored.

In the example above I made a copy Basic 1 of the Basic theme and arbitrarly disabled and enabled settings in the various tabs.



The initial settings for the various default profiles (Basic, Man Page, Ocean etc.) are stored in the app itself:

/Applications/Utilities/Terminal.app/Contents/Resources/Initial Settings/

The *.terminal files are basically XML-files. They are imported into the ~/Library/Preferences/com.apple.Terminal.plist as sub-items on the first launch of Terminal.app.