When editing, hold shift to select multiple points. Hold Ctrl to add an extra point along an edge. To add points to either end of the sequence, first select either the first or last point and then hold Ctrl. Backspace deletes currently selected points. In edit mode, holding Shift generally toggles the snapping behavior (makes it opposite of the current SnappingEnabled setting), though this is not yet implemented while the gizmo is being dragged.