The Scissors tool separates both open and closed paths, but the new paths it creates are always open.
Hold Shift and drag to constrain the angle of the cut line.
Aligning Points and Segments Horizontally or Vertically
Aligning Points and Segments to an Angle
Acquiring and Applying Length and Angle
Converting Segment into a Curve
Converting Segment to Smooth Arc
Converting Segment to 3-Point Arc
Converting Segment to Arc
Eliminating Extra Points
Removing One Point
Adding One Point
Changing Starting Point
Separating to Closed Paths
Converting Corners to Right Angle
Removing Tiny Objects