In the old versions of Cubase one could open the list editor with Ctr+G. In Cubase 9,5 the only way is to go to MIDI and then choose it from the menu. Can I not build a shortcut? It used to be so convenient.
You can configure keystrokes to almost every menu item in Cubase. Open the Key Commands Dialog and search for List Editor (or anything else you want to add a keystroke to.) 
Tank you Steve! I did it! 