The trick is to generate a suitable equivalent circuit for the human body interface.
If this resulting circuit comprises of passive device like R, L, C, diodes and active devices (semiconductors), then KiCAD/ngspice can simulate this interface. Some of the pictures you have shown point into this direction.
The choice is yours! You will have to define/select such a circuit, draw it in KiCAD/Eeschema, and off you go.