Library organization is very important since ArchiCAD relies on "Loaded Library Parts"...
Before doing any major changes to your ArchiCAD Libraries, you should create .PLA files of all current and past projects. This will "embed" the used Objects into the archive file and will allow you to access them whenever you access the file.
I recommend investing some time creating and organizing a company/personal ArchiCAD Library. This is where you would store all of your custom and/or purchased objects that are not part of the standard "out-of-the-box" libraries.
If you have the time, streamline the standard current libraries, removing unused Objects. You can easily figure out how much of your libraries you are using by creating .PLA files of current projects and opening the archive file and extracting the imbedded Objects. (Hint: Macro Objects don't get archived by default so be careful with the "Macros" folders).
Every project should have it's own Library, located in the same folder as the project file. This Library stores project specific Objects like stairs.
Anytime you have a Library that you are not editing or altering it is best to keep it in .PLA format. .PLA libraries tend to load faster than expanded folder libraries.
The "Others" folder that you refer to indicates Objects that have been inserted into the project but don't physically reside in any of the "Loaded Libraries". Those objects should be saved or moved to a loaded Library to alleviate future problems.
If you are sharing a .PLN file with others on separate computers that are not networked each computer would need to have duplicate Libraries. Using the .PLA method of file sharing could help.
Again, I reiterate, ArchiCAD Library organization and maintenance is very important.
David Larrew, AIA, GDLA, GSRC
Architectural Technology Specialist
a r c h i S O L U T I O N S
WIN7-10/ OSX 10.15.7
AC 5.1-25 USA