Auto login
From Exilent
Auto login keeps track of your already logged in accounts and types your login info automatically in the login screen.
When having the Auto login turned on after clicking Existing User the login details will be automatically filled and Enter key will be sent.
To add a new account turn off Auto login so you can type the login details of a new account.
To remove accounts right click on them.
Security
Login info is not stored on your computer or in the cloud, it is just read from the client (username and password field in the game's code) - any third party client can do this already.
Setting up
Settings - General - Enable auto login