Drum editor does not show the drum sound list

I’m using Cubase 8.5 in Win7. My Project contains a midi track with a custom drum map selected. I cannot exactly tell how I managed it but now the drum editor does not show up the drum sound list anymore. Is the drum sound list somehow hideable? How can I make it reappear?
However the events in the track show up and play correctly, also the info line displays the correct name of the sound in the selected map.
I restarted Cubase 8.5, created a new project with a the GM Map but still there is no drum sound list visible.
I opened the project with my drum map in Cubase 8.0 and found the drum editor displaying the drum sound list correctly. Did I somehow reconfigure my Cubase 8.5?

Please could anyone tell me, what I did wrong and how I can get the drum sound list back?