From FreeCAD Documentation
- Select a B-spline.
- There are several ways to invoke the tool:
- Press the Insert knot button.
- Select the Sketch → Sketcher B-spline tools → Insert knot option from the menu.
- introduced in version 1.0: Right-click in the 3D view and select the Insert knot option from the context menu.
- Move the cursor to the desired location.
- The current position is marked with a small circle and its parameter value is indicated.
- Click to insert a knot, or click an existing knot to increase its multiplicity.
- This tool always runs in continue mode: optionally keep inserting knots and/or increasing multiplicity values.
- To finish, right-click or press Esc, or start geometry or constraint creation tool.