When ticking the general preference to "double click on media file loads into Trimmer instead of tracks", I expect this to work, but it still drops my clips to the timeline tracks. It seems to work fine if you have a default layout, but if you have a personalized layout, it does not work, the trimmer window remains empty. It is a bug that is easy to reproduce.
It does not seem to be limited to V15, but also applies to V14 

my layout <> default layout