The system value SL LoginEnvironment is available for use in Event Rules. So it can be used in an application or UBE.
If, however, what is required is for a user who is logged on to JDE to find out the environment in which he/she is working then:
1) For fat clients, ensure that the status bar is at the bottom of the screen (toggle on/off via View Menu). In the status bar, on the right, the User ID and Enviroment are displayed, along with other information. Another way is to use the On-Line Support Information application (P00890) and click the "Details" button at the bottom right of the window. This will display a window of information which include the Enviroment. Access to P00890 can be direct via fast path (enter P00890) or from the Help Menu and menu item About JDE. The preceding may vary depending on the tools release in use - this is the situation for tools release 8.96.C1.
2) For web clients, clicking the "i" button at the top right of any application will provide a window of information. At the bottom of that window, under the heading "Other" is the EnterpriseOne (Tools) Release, User ID and Environment. This may vary depending on the tools release in use - this is the situation for tools release 8.96.C1.