If you want to back up your Chromium folder it is in a hidden folder in your home directory. Mine is /home/cavsfan/.config/chromium. Drop that into your new userid's home directory in .config folder and it will retain all of your settings: bookmarks, extentions, cookies, etc.
Just FYI: the folder for Firefox in in the home directory .mozilla and Thunderbird is in .thunderbird.
Bookmarks