How to summarize movie files?

I am new to Kodi and I like it very much. Thank you for this great software! Everything is working fine but I have one annoying problem which I can’t resolve.

I have ripped some of my blu-rays with MakeMKV and put the resulting mkv files on my NAS to watch them via Kodi. Every movie consists of a few mkv files (main movie + features etc.). The problem is that in Kodi’s movie library all mkv files of one movie are represented as independent movies. Is it possible to summarize them? Furthermore I have movies which consists of a single file. My directory structure on my NAS looks like

Code:
movie1/movie1_a.mkv
      /movie1_b.mkv
      /movie1_c.mkv
movie2/movie2_a.mkv
      /movie2_b.mkv
      /movie2_c.mkv
movie3.mkv
movie4.mkv
...