When writing with MIDI Keyboard, Undo (CTRL+Z) should apply to entire chords instead of one note at a time
The regular way of deleting long passages of chord progressions = Hit Undo repeatedly to remove one note a time in a chord or cluster of chords OR, if you were Notating, Unclick Notate, Shift+Click or Shift+left/right chords or passage of chords and hit delete, click notate AGAIN if you want to start writing again from where you were.
Suggested way of undoing chords: If Undo applies to entire chords, just spam Undo, eliminating unnecessary clicks and shift+clicks.