This popup displays the list of variables used for runtime. These variables are set when you execute a program, or debug a program. This environment is also set when you opens a Runtime Window (Menu Tools/Open RuntimeWindow). There are 2 kinds of variables: Basic variables can not be modified, and User variables where you can add and define your own environment variables for runtime. When you add a User variable, it is automatically available for program execution or for debug, but not in Runtime windows (re-open it to take the new variable into account).