From FreeCAD Documentation
- If you don't select any shape in the first step, you will be tracing the shape that was selected in the third step.
- To change the element to trace, you need to disable this tool before selecting a new element and enabling it again.
- If you control the movement with another tool such as this kinematic controller that allows to use a mover tool in parallel, you could use this tool to alter the assembly step by step and use the mover tool to add a point and connecting line on each step. It is possible to use the mover tool as a trigger by picking and dragging any of the arrows - just a tiny bit until the next point and line appears (use transparency if necessary).
- (I hope there will be a more elegant way in the future)