The Drum Editor was made to work with Drum Maps. If you mix mapped and non-mapped, it may have to open one edit window for each map and one for all unmapped tracks.
The Key Editor shows the entire range of MIDI notes. Both mapped and unmapped tracks can be displayed in one edit window, since the limit of maps are the MIDI note range.
In either case, you may have to scroll to see MIDI events from different tracks.
"Remember that we live only in the present, in this fleeting instant; all the rest of our life is either past and gone, or not yet revealed."