How to save group of textures as a local collection?

I’m new to Sketchup and currently trying to figure this out? The tutorials I see online use Windows and I’m using MacOS (2020 version) and I can’t figure out how I’m supposed to do it with my operating system.

If you have a collection of In Model materials that you want to save as a Local Collection, display the In Model materials and in the lower part of the Colors panel click Duplicate in the List drop down. Then you can give it a name if you want.

On Mac, collections of textures or colors are called “lists”. Manipulate them using the List button in the lower part of the materials (aka “Colors”) window.

SketchUp on Mac uses the native colorpanel of the OS.
It uses lists instead of ‘folders’ on Windows.
Upon startup, they load from three possible locations, the user library, the general library and the packaged content in the app itself if something is missing from the standard set of lists.
The standard set of lists is what you see in the panel, if you want to create your own list, you must click on the ‘in model’ button (little house) and duplicate the materials list.
This list will be saved in the user library (~/Library/SketchUp/SketchUp 2021/SkerchUp/Materials

The stand lists won’t show there and you cannot create subfolders.
The newly created folder contains the .skm files.

Note: in addition to what @MikeWayzovski wrote, you can choose a different location via SketchUp->Preferences->Files. This is useful to share your lists between different versions of SketchUp.