You can use any of the standard deletion techniques to delete events in the Step Editor.
Do one of the following:
Click the step with the Eraser tool.
Click the step, then press Delete.
Drag across the steps you want to delete with the Eraser tool.
Shift-click the steps you want to remove, then press Delete.
Select one of the steps you want to delete.
Use the Select Similar Regions/Events (Shift-S) or Select Equal Regions/Events (Shift-E) key command, then press Delete.
You can also delete events by choosing one of the Delete MIDI Events commands from the Step Editor menu bar. For more information, see Delete notes in the Piano Roll Editor.