Solution : https://service.sap.com/sap/support/notes/1617641 (SAP Service marketplace login required)
Summary : 
      SAP Note addresses logon control challenges with scenarios where users need an SNC logon without employing Single Sign-On in SAP Logon. Solutions provided include kernel enhancements and GUI updates; a new context menu for "SNC Logon without Single Sign On" and a checkbox for "SNC Logon with User/Password (no Single Sign-On)" in Secure Network Settings. The entry necessitates user credentials for logon. The resolution involves an update via a SAP GUI for Windows patch, with details on patch downloading and installation guidance available on SAP Service Marketplace and through specific SAP documentation notes.
Key words : 
threadid=449137&tstart=0 downloading sap gui patches, prerequisites program error solution, /irj/sdn/sap-gui, context menu entry added, sap gui installation guide, terms sap gui, sap gui patches, sap gui extension, sap developer network, sap service marketplace
Related Notes : 
       
| 1616598 | Enabling RFC password logon despite SNC | 
| 1561161 | |
| 1053737 | Expected release dates for SAP GUI for Windows & ITS Patches | 
| 563161 | SAP GUI, SAP ITS & SAP IGS patches on Service Marketplace | 
| 535308 | How to apply a SAP Front End patch? | 
| 330793 | Downloading patches |