Saved settings
Keeping a set of settings and putting it on another session.
Saving and loading
Save as keeps everything on screen under a name, including changes you have not saved yet. Load puts a saved set onto the session you are looking at, which is the quick way to give a new Google account the same behaviour as an old one.
Saved settings belong to your account rather than to one session, so they show up on every session you own.
Once you have saved a set, Start with appears beside the button that connects a Google account. It picks the set a new session begins with, and your choice is remembered for next time. If that set is ever deleted, new sessions go back to Default.
The Default set
Default is built from the starting values the people running this site have set, so it is always there and cannot be deleted. Load it to put a session back to a sensible starting point.
The line under the list tells you which set a session is using, and whether it has drifted since you loaded it.