Where does Nautilus store bookmark names?
They are stored in the ~/.config/gtk-3.0/bookmarks file
In older versions of Ubuntu they are stored in the ~/.gtk-bookmarks file.
The format is:
file:///path/to/folder Bookmark_name
You can also specify other location protocols such as SFTP, FTP, or SMB:
sftp://username@hostname/path/to/folder Bookmark_name