The library tables tell kicad where libraries are and under which name (nickname) the libraries should be addressed. (The nickname defines the name used by kicad, the path is the name used by the operating system)
Yes only libraries that are in the lib table are known to kicad. If your library is not in the library table then kicad does not know about it.
Again read Creating a new footprint library with the support of
Library management in KiCad version 5 and Tutorial: How to make a footprint in KiCad 5.1.x?