May be you all must be knowing it but i found it very useful ( since habbit of forgetting password 
) so thought of sharing this with you .So that you can quickly open and close sessions without wasting time in manually typing password or selecting the environment.
Create a new SAP shortcut, for the system you want to logon.
As you can see above, By default SAP disabled the ability for users to save password. To enable it you need to tweak your Windows Registry
Steps -
1. Enable Password Field in SAP – .
- Start -> Run -> type “REGEDIT”
- In the Registry, navigate to HKEY_CURRENT_USER > SOFTWARE> SAP
- Right click on SAP folder, then use select NEW > Key and name it “SAPShortcut”
- Perform the last step but this time create a key called “Security”
- Right click on Security then New > String Value. Name the string EnablePassord
- Double click on EnablePassword and enter ’1′ in the Value Data field, then press OK and close Registry
1.Open the SAP logon screen, then click ‘New Item’ button.
2. In the ‘Create New SAP Shortcut’ window fill in the title, user, password fields. Select the System Description manually using the drop down, then press next
As you can see above ,Password is enabled now 
3.In the next screen keep the working directory as default ( no need to change ). Adjust the Window Size based on your preference and once complete please press 
and your shortcut should appear on the SAP logon screen and also on your desktop.
Next time you double click on the shortcut on the SAP Logon Pad, it will use the saved password from the text file
and won’t ask you for a password. And if your password is changed you can update in that shortcut directly by right click-->properties and give new password and close it simple .
Hope it proves Useful
Best Regards,
Praveen Srivastava