documentclass[11pt,titlepage,oneside,openany]{book}
    usepackage{forest}
    begin{document}
    begin{forest}
    [A, name=a[B][C[D][E ,name=e[F][G]]]]
    end{forest}
    end{document}

documentclass[11pt,titlepage,oneside,openany]{book}
usepackage{forest}
begin{document}
begin{forest}
[A,name=a
 [B]
 [C
  [D]
  [E ,name=e
   [F]
   [G]
  ]
 ]
]
draw[thick,-latex] ([xshift=1cm]a.north east) -- ([xshift=1cm]e.south east)
node[midway,sloped,above]{text on arrow};
end{forest}
end{document}