Library modules are compiled independently of forms, and thus the values of global variables are out of scope of library program units (you cannot access them directly).
However, you can use the NAME_IN built-in function to reference them.
For example, instead of:
Reference the value of the variable this way:
If you want to set the value of the global variable inside your library program units, you can use the COPY built-in procedure, for example:
But, I would prefer to create the library procedures with parameters (IN or OUT) to pass data between forms and the library, instead of using global variables this way.