I want to draw a minimal box which contains all the `grandchild`s (pink boxes), ![enter image description here](https://i.stack.imgur.com/a2bxb.jpg) and move the text of deep green box to the bottom of the new box. How could I do it?

codes:

```
\documentclass{standalone}
\usepackage{forest}
\usetikzlibrary{arrows.meta,shapes,positioning,shadows,trees}

\tikzset{
    basic/.style  = {draw, text width=2cm, drop shadow, font=\sffamily, rectangle},
    basic1/.style  = {draw,  drop shadow, font=\sffamily, rectangle},
    root/.style   = {basic, rounded corners=2pt, thin, align=center,                    fill=green!30},
    onode/.style = {basic, thin, rounded corners=2pt, align=center, fill=green!60,text width=3cm,},
    tnode/.style = {basic1, thin, align=left, fill=pink!60},
    edge from parent/.style={draw=black, edge from parent fork right}
}
%
\begin{document}
\title{Structure of Book}
\begin{forest} for tree={anchor=base west,
    grow=east,
    growth parent anchor=east,
    parent anchor=east,
    child anchor=west,
    edge path={\noexpand\path[\forestoption{edge},->, >={latex}] 
         (!u.parent anchor) -- +(5pt,0pt) |- (.child anchor)
         \forestoption{edge label};}
}
[Nonlinear Stochastic Systems, root
       [{Applications to Complex Systems, NCSs, GRNs}, onode
       [Chapter 8\\ Complex Networks, tnode]
        [Chapter 7\\ Networked Control Systems, tnode] 
        [Chapter 5\\Gene Regulatory Networks, tnode] ] 
]
\end{forest}
\end{document}

```