Google-chrome – Why is Google Chrome not saving proxy username/password

Try the --proxy-server command line option, and/or http_proxy environment variable.

google-chrome-stable --proxy-server="http://example.com:8080"

Also, Chrome/Chromium makes use of xdg scripts, so you can try configuring the proxy server in GNOME/KDE, and set up xdg scripts to use settings of the desktop environment. That is how I solved MIME-type file associations at least.

Go to Options → Personal Stuff → Manage Saved Passwords, hover over what you want to delete, and then click the x.

UPDATE (credits to camster342): It's now in Settings -> Show Advanced Settings... and Manage Passwords is the second link under the Passwords and Forms section.

If the data you want to delete is not a password but rather a saved form follow this:

When you type in a form field, a menu may appear, containing past text that you've typed in the field. To delete a specific piece of saved text, select it in the menu using the arrows on your keyboard, then press Shift+Delete.

_(source)

On Mac OS it's Fn+Backspace or Fn+Shift+Delete.