The most efficient way is have your materials stored somewhere other than the default library location.
This saves you pain if/when you upgrade to major releases.
On Mac go to SketchUp > Preferences from the menu bar and set the path to where you will stored you materials.
Place your materials, typically folder separated based on category/type, into that location.
https://help.sketchup.com/en/sketchup/setting-software-and-file-preferences
https://help.sketchup.com/en/sketchup/adding-colors-and-textures-materials#manage-material