There is no such single view-it-all screen in MIDI editor, but you could fake something similar e.g. like this:
1) Create a new track with an empty MIDI item covering the whole length of the project. In MIDI editor, select this track/item as a target for inserting events. This will be your empty background where all the other items/events will show up.
2) In MIDI editor Track Selector, make all the tracks/items which you want to see visible and editable by clicking the eye and lock icons.
You'll have to have
One MIDI editor per project and
Open all MIDI in the project set up in the MIDI Editor preferences.
https://imgur.com/jm54rDu