How can I display the variables of a library linked to my file in the plugin interface?

Good community! I’m trying to display in the plugin interface the variables available in a file. The local variables do not give me any problem, but those that are available through an external library linked to the file, I can not get them to be displayed in the plugin interface. I just wanted to know if someone encountered this case or someone who can give me more light because I do not know if it is a limitation of the Api or something that I can not understand. Thank you very much in advance