How to save a group/component and use it again in?

[Shadowbluff]

So, how does one do this so they can be used again in another project? Is it possible?

Thanks!

[TIG]

You can use Edit>Copy and Edit>Paste or PasteInPlace on anything in one SKP and thereby duplicate it in another SKP.
You can't readily reuse a Group in another SKP later on, unless you convert it to a Component [context-menu item]...
The usual way to make one SKP's Components available for use at any time later, is to open the Component Browser and either Save an individual Component [you can also do this for a selected instance, from a context-menu item] or you can choose the flyout menu option to Save all of your Components to a Collection.
You can delete any unwanted SKPs from that folder...
That Collection [aka Library] can be made accessible from the Component Browser, so that you can use those Components in future projects...
If you are thinking of keeping all of your Component SKPs in a single location then ensure you have FULL Security permissions to that folder - the standard SketchUp/Components folder might have limited permissions by default...