From Synfig Studio :: Documentation
- Pressing to select all Handles
- Dragging a rectangle around a group of Handles
- Holding the key while clicking Handles to toggle their selected status
Then drag one of the selected Handles. All the selected Handles will move, rotating about the center of the selected group.
The "Rotate Tool" has a tool option, "Allow scale", to allow the selected Handles to be scaled and rotated at the same time.