How to set straight line (horizontal) connector?

Question

Please help me to set a straight line (horizontal) connector. Thank you in advance.

\documentclass[a4paper,11pt]{article}
\usepackage[edges]{forest}
\usepackage{caption}
% Source <------------- https://tex.stackexchange.com/questions/300373/saving-horizontal-space-in-tree-diagram


%Defining tikz classes for tree diagrams
\tikzset{parent/.style={align=center,text width=3cm,rounded corners=3pt},
    child/.style={align=center,text width=3cm,rounded corners=3pt}
}
\colorlet{col1}{white}
\colorlet{col2}{gray!20}
\colorlet{col3}{gray!40}
\colorlet{col4}{gray!60}
\begin{document}
    \begin{center}
        \resizebox*{.75\linewidth}{!}{%
            \begin{forest}
                forked edges,
                for tree={
                    grow'=east,
                    draw,
                    rounded corners,
                    text width=2.7cm,
                    node options={align=center},
                }

                [TEXT, fill=col4, parent, s sep=1cm
                [TEXT TEXT, for tree={child, fill=col3}
                [TEXT\ TEXT, for tree={child, fill=col2}
                [{TEXT\ TEXT, TEXT \ TEXT, TEXT \ TEXT, TEXT \ TEXT, TEXT \ TEXT}]]
                [TEXT \ TEXT, for tree={child, fill=col2}
                [{TEXT \ TEXT, TEXT \ TEXT}]]
                [TEXT-\TEXT, for tree={child, fill=col2}
                [{TEXT \TEXT, TEXT \TEXT}]]
                [TEXT\TEXT, for tree={child, fill=col2}
                [{TEXT \TEXTg, TEXT \TEXT}]]
                [TEXT\ TEXT, for tree={child, fill=col2}
                [{TEXT \TEXT, TEXT \TEXT}]]
                ]
                [TEXT TEXT, for tree={child, fill=col3}
                [TEXT\ TEXT, for tree={child, fill=col2}
                [{TEXT\ TEXT, TEXT \ TEXT, TEXT \ TEXT, TEXT \ TEXT, TEXT \ TEXT}]]
                [TEXT \ TEXT, for tree={child, fill=col2}
                [{TEXT \ TEXT, TEXT \ TEXT}]]
                [TEXT-\TEXT, for tree={child, fill=col2}
                [{TEXT \TEXT, TEXT \TEXT}]]
                [TEXT\TEXT, for tree={child, fill=col2}
                [{TEXT \TEXTg, TEXT \TEXT}]]
                [TEXT\ TEXT, for tree={child, fill=col2}
                [{TEXT \TEXT, TEXT \TEXT}]]
                ]
                ]
                ]
                ]
        \end{forest}}
        \captionsetup{type=figure}
        \captionof{figure}{Caption.}
        \label{tikz:taxonomy}
    \end{center}
\end{document}

Answer 1

\documentclass[a4paper,11pt]{article}
\usepackage[edges]{forest}
\usepackage{caption}
% Source <------------- https://tex.stackexchange.com/questions/300373/saving-horizontal-space-in-tree-diagram


%Defining tikz classes for tree diagrams
\tikzset{parent/.style={align=center,text width=3cm,rounded corners=3pt},
    child/.style={align=center,text width=3cm,rounded corners=3pt}
}
\colorlet{col1}{white}
\colorlet{col2}{gray!20}
\colorlet{col3}{gray!40}
\colorlet{col4}{gray!60}
\begin{document}
    \begin{center}
        \resizebox*{.75\linewidth}{!}{%
            \begin{forest}
                forked edges,
                for tree={
                    grow'=east,
                    draw,
                    rounded corners,
                    text width=2.7cm,
                    node options={align=center},anchor=parent
                }

                [TEXT, fill=col4, parent, s sep=1cm
                [TEXT TEXT, for tree={child, fill=col3}
                [TEXT\ TEXT, for tree={child, fill=col2}
                [{TEXT\ TEXT, TEXT \ TEXT, TEXT \ TEXT, TEXT \ TEXT, TEXT \ TEXT}]]
                [TEXT \ TEXT, for tree={child, fill=col2}
                [{TEXT \ TEXT, TEXT \ TEXT}]]
                [TEXT-\TEXT, for tree={child, fill=col2}
                [{TEXT \TEXT, TEXT \TEXT}]]
                [TEXT\TEXT, for tree={child, fill=col2}
                [{TEXT \TEXTg, TEXT \TEXT}]]
                [TEXT\ TEXT, for tree={child, fill=col2}
                [{TEXT \TEXT, TEXT \TEXT}]]
                ]
                [TEXT TEXT, for tree={child, fill=col3}
                [TEXT\ TEXT, for tree={child, fill=col2}
                [{TEXT\ TEXT, TEXT \ TEXT, TEXT \ TEXT, TEXT \ TEXT, TEXT \ TEXT}]]
                [TEXT \ TEXT, for tree={child, fill=col2}
                [{TEXT \ TEXT, TEXT \ TEXT}]]
                [TEXT-\TEXT, for tree={child, fill=col2}
                [{TEXT \TEXT, TEXT \TEXT}]]
                [TEXT\TEXT, for tree={child, fill=col2}
                [{TEXT \TEXTg, TEXT \TEXT}]]
                [TEXT\ TEXT, for tree={child, fill=col2}
                [{TEXT \TEXT, TEXT \TEXT}]]
                ]
                ]
                ]
                ]
        \end{forest}}
        \captionsetup{type=figure}
        \captionof{figure}{Caption.}
        \label{tikz:taxonomy}
    \end{center}
\end{document}