Bitwig's note editor offers two quick ways to duplicate MIDI notes: Alt/Option-drag to copy a selected note by dragging it to a new position, or Cmd+D to duplicate it repeatedly in place. Both shortcuts are standard, but the range duplication behavior is where things get more useful.
Selecting a range that includes blank space before hitting Cmd+D copies that entire region as-is, preserving the gaps. This keeps your timing and spacing intact when you need to loop or extend a pattern.