GDL objects only know about themselves (there are some global variables and REQUESTS to get info about parent objects).
You can manipulate the parameter values in the parameter script using the PARAMETERS command. But be aware that the parameter script is only run after user input – changing a setting, placing a new instance.
The library MVO approach is good if you write your own set of objects that read the settings written by you. You can’t add new MVO settings to control the ArchiCAD Library.
If you need to change the behaviour of the shipped ArchiCAD library programmatically, you will need to write an Add-on in C++ using the ARCHICAD API.
Library Platform, Software Engineer