How to control the vertical space between the parent and the first child inside a forest environment

Question

Based on the answer https://tex.stackexchange.com/a/270761/278762 from @GonzaloMedina. How can I control the vertical space y shown in the picture below

CODE:

\documentclass[border=5pt]{standalone}
\usepackage{forest}
\begin{document}
\begin{forest}
  for tree={
    font=\ttfamily,
    grow'=0,
    child anchor=west,
    parent anchor=south,
    anchor=west,
    calign=first,
    edge path={
      \noexpand\path [draw, \forestoption{edge}]
      (!u.south west) +(7.5pt,0) |- node[fill,inner sep=1.25pt] {} (.child anchor)\forestoption{edge label};
    },
    before typesetting nodes={
      if n=1
        {insert before={[,phantom]}}
        {}
    },
    fit=band,
    before computing xy={l=15pt},
  }
[text1
  [text1.1
    [text1.1.1]
    [text1.1.2]
    [text1.1.3]
  ]
  [text1.2
    [text1.2.1]
    [text1.2.2]
  ]
]
\end{forest}
\end{document}

OUTPUT:

Answer 1

If you want to change the spacing for all the children of text1.1, you can simply change s sep:

[text1
  [text1.1, s sep=1cm
    [text1.1.1]
    [text1.1.2]
    [text1.1.3]
  ]

On the other hand, if you only want to change the spacing above text 1.1.1, then you can add yshift= to the node:

[text1
  [text1.1
    [text1.1.1, yshift=-1.5cm]
    [text1.1.2]
    [text1.1.3]
  ]

If you want to do this for all the x.x.1 nodes, you can add it to the for tree:

if n children=0{if n=1{yshift=-1.5cm}{}}{}

Here is the complete code:

\documentclass{article}
\usepackage{forest}
\begin{document}
\begin{forest}
  for tree={
    font=\ttfamily,
    grow'=0,
    child anchor=west,
    parent anchor=south,
    anchor=west,
    calign=first,
    edge path={
      \noexpand\path [draw, \forestoption{edge}]
      (!u.south west) +(7.5pt,0) |- node[fill,inner sep=1.25pt] {} (.child anchor)\forestoption{edge label};
    },
    before typesetting nodes={
      if n=1
        {insert before={[,phantom]}}
        {}
    },
    fit=band,
    before computing xy={l=15pt},
    if n children=0{if n=1{yshift=-1.5cm}{}}{}
  }
[text1
  [text1.1
    [text1.1.1]
    [text1.1.2]
    [text1.1.3]
  ]
  [text1.2
    [text1.2.1]
    [text1.2.2]
  ]
]
\end{forest}