It is possible to specify the username and password within the Plesk login link to allow automatic login, the link needs to look like this:

https://aries.magdesign.co.uk:8443?login_up.php3?login_name=domainname&passwd=pleskpassword

For example:

https://aries.magdesign.co.uk:8443?login_up.php3?login_name=test.com&passwd=qwerty

You can then add this link to your favourites for quick access to Plesk.