How to Log in as different domain user in Microsoft Dynamics AX 2012
You can run/log on in AX 2012 as a different user simply by holding shift and right clicking on the AX 2012 launch icon.
This will bring up a menu option “Run as different user” with which you can supply alternate credentials.
AX 2012 allows multiple log in instances for the same user so this can be handy for troubleshooting and user support. Request to please check these screen shots: