(in terms simple, please, my english is not really good)

Not mine either!
1. Have You read this "Guida Utente" in italiano?
2. SH3D have 2 kind of furniture library:
-some come with default program;
-some could be imported (installed) optionally
3. The simplest way is to remove (delete) entire imported library.
All library can be modified but I can't explain in simple terms even in Romanian.
You have to discover how a furniture library work and what You can modify.
Sorry I'm not able to help You more.