1.Why is there not a CAD-Line in the Base-Part?
We do not want you to automatically add Joints to the Origin of the Base-Part.
However, you are welcome to do this.
For the Base-Part, we have found it to be useful to add Points and Lines that are not at the Origin or along the X-axis or Y–axis.
You can edit the dimensions later, and also add the dimensions to a Design-Set.
4.Why edit Points and Lines in the Base-Parts?
a.Edit the dimension and move the Joints, if the Points or Lines are used for Joints
b.Move the Plane and Mechanism-Editor in the Machine Frame, if a Line is used for a new Plane and Mechanism-Editor.