The composition rules of period-tripling and period-doubling in symbolic dynamics of four letters are proposed. The methods to generate various singly and doubly superstable kneading sequences from triply superstable kneading sequences are given. These composition rules and methods will present all the essential elements in the three-dimensional parameter space, including the `joint', `bones', `membrane surfaces' on the `skeleton' and many fractal objects constructed by period-doubling and period-tripling bifurcations. It is shown that the generalization from unimodal and bimodal to trimodal maps is not trivial. And the promptly exponential growth in the kinds of star transformations is even seen when the number of critical points (or parameters) of the map increases.