Libraries. Don't new projects create their own library to store it's symbols

This might be of interest Project and libary setup for sharing and collaboration (KiCad version 5) (TlDr: how your setup will look like highly depends on what you want to achieve. There is not one single answer.)

And for version 5 and earlier also this What are the cache and rescue libs and how does the schematic rescue dialog work? (KiCad version 5.x and earlier)