How do I get iTunes to make more playlists like it did before?

Once you have a library (which you would after the using the Import option), future music should be added using the "Add Music to Library" option. At least, that's how it works on my Mac.

I had no problem adding it to the library, but the automatically generated playlists that it made when I first added music the library did not occur, like it did with the first installment of music.

I have never had iTunes automatically create playlists for artists and albums. Are you sure the playlists did not already exist, and were simply imported along with the songs themselves? In any case, in the iTunes browser, find the artist or album you want, and then drag it to the Source column to automatically create a playlist.

I never heard of this. Anyway, why create playlists for each album/artist? iTunes already lets you group and browse that way pretty easily. I prefer to save my sidebar space for real playlists that involved effort and imagination to create, not playlists that are just made up of album tracklists.

I think you might be misusing the term "playlists". What exactly did iTunes do when you imported the first batch, and what did it do different the second time? Whereabouts in the iTunes window did these "playlists" appear?