There have been quite a few discussions about library structure; try a search.
You should never put library parts from other sources in the archicad library. Some updates may overwrite the whole library file and then these would be lost
Archicad Library
Project Library - objects specific to the project such as stairs
Office Library - objects used on multiple projects
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"