Copying the Theme
It is possible to copy the theme settings via an "export" function, and then "import" it somewhere else. Two good examples of this are:
To import the English theme in the French theme as a starting point
To import a theme from staging to production once you've completed your changes on staging
Step-by-step guide
The sections below explains how to both export and import the theme settings/
To export your theme:
Go to Site Administration > Appearance > Themes > English (or French) > Import / Export Settings
Click on the "Export Properties as a JSON string" button
Using your mouse and cursor, select the whole JSON string and copy it (CTRL+V)
NOTE: The JSON string does not contain any files or images. It strictly contains the settings.
To import your theme:
Go to Site Administration > Appearance > Themes > English (or French) > Import / Export Settings
Scroll down to the very bottom of the page until you see the "Import Properties" section
Paste the JSON string you exported previously (CTRL+V) in the "Import Properties"
Click on the "Save changes" button
NOTE: Once you save the settings, you will still need to import other files and images (e.g. logo, favicon, etc.) manually.