Alignment problem with title in rather complex tcolorbox

Question

I'm trying to align the main title so it starts after the counter box [red] and runs towards the right side of the box, but so far it stretches to the left. What am I doing wrong? Merci in advance for any help.

MWE:

\documentclass[11pt,a4paper]{article}
\usepackage[utf8]{inputenc}%erlaubt Umlaute
\usepackage{lmodern}
\usepackage[skins]{tcolorbox}



\newtcolorbox[auto counter, ]{mybox1}[3][]{
  enhanced,
  arc=.3mm, 
  boxrule=0.3pt,
 fonttitle=\bfseries,
  colback=white,
  colframe=red!65!black,
  enlarge top by=10mm,
  subtitle style={ boxrule=0.2pt,
  colback=blue!40!white}, 
  overlay={%
    \path[fill=blue!65,line width=.4mm] (frame.north west)--++(17mm,0)coordinate(n2)--++(0,8mm)--++(-20mm,0) arc (-90:90:-4mm)--cycle;
    \node at ([shift={(5mm,4mm)}]frame.north west){\color{white}{
        \textbf{\sffamily  #2}}};
    \path[fill=red!65!blue] ([xshift=.4mm]n2)--++(0,8mm)--++(7mm,0)--++(0,-8mm)--cycle;
    \node at ([shift={(4mm,4mm)}]n2){\color{white}{\textbf{\sffamily \thetcbcounter}}};
    \node at ([shift={(18mm,4mm)}]n2){
     \itshape\textbf{\sffamily #3}};
  },
  #1
}

\newcounter{mycounter}

%----------------------------------------------------------------------------------------
%TCOLORBOXES
%----------------------------------------------------------------------------------------


\begin{document}


\begin{mybox1}[label=one]{sample}{Gebäudeheizlast nach DIN 12831 nach Temperatur}
This is a \textbf{tcolorbox}.\par
a lot of text here ... This is Example \ref{one}
\tcbsubtitle{\textbf{ Formeln}}
some text
\end{mybox1}

\end{document}

Answer 1

The quickest solution is to select the correct anchor for title positioning (default is center) and the desired xshift. This is what is done in mybox1 in following code.

A more elaborated solution consists in replacing filled paths with superposed nodes by three nodes placed with positioning library. The left node is a rounded rectangle from symbols.misc library. Finally, text and font options has been used to adjust aspect of nodes' contents. This is what is shown in mybox2.

\documentclass[11pt,a4paper]{article}
\usepackage[utf8]{inputenc}%erlaubt Umlaute
\usepackage{lmodern}
\usepackage[skins]{tcolorbox}
\usetikzlibrary{positioning, shapes.misc}

\newtcolorbox[auto counter, ]{mybox1}[3][]{
  enhanced,
  arc=.3mm, 
  boxrule=0.3pt,
 fonttitle=\bfseries,
  colback=white,
  colframe=red!65!black,
  enlarge top by=10mm,
  subtitle style={ boxrule=0.2pt,
  colback=blue!40!white}, 
  overlay={%
    \path[fill=blue!65,line width=.4mm] (frame.north west)--++(17mm,0)coordinate(n2)--++(0,8mm)--++(-20mm,0) arc (-90:90:-4mm)--cycle;
    \node at ([shift={(5mm,4mm)}]frame.north west){\color{white}{
        \textbf{\sffamily  #2}}};
    \path[fill=red!65!blue] ([xshift=.4mm]n2)--++(0,8mm)--++(7mm,0)--++(0,-8mm)--cycle;
    \node at ([shift={(4mm,4mm)}]n2){\color{white}{\textbf{\sffamily \thetcbcounter}}};
    \node[anchor=west] at ([shift={(8mm,4mm)}]n2){
     \itshape\textbf{\sffamily #3}};
  },
  #1
}

\newtcolorbox[auto counter]{mybox2}[3][]{
    enhanced,
    arc=.3mm, 
    boxrule=0.3pt,
    fonttitle=\bfseries,
    colback=white,
    colframe=red!65!black,
    enlarge top by=10mm,
    subtitle style={ boxrule=0.2pt,
    colback=blue!40!white}, 
    overlay={%
        \node[fill=blue!65, rounded rectangle, rounded rectangle right arc=none, anchor=south west, text=white, font=\bfseries\sffamily, minimum width=24mm, minimum height=8mm] at (frame.north west) (n2) {#2};
    \node[fill=red!65!blue, right=0pt of n2, minimum height=8mm, minimum width=7mm, text=white, font=\bfseries\sffamily] (n3) {\thetcbcounter};
    \node[anchor=west, right=0mm of n3, minimum height=8mm, font=\bfseries\itshape\sffamily] {#3};
  },
  #1
}

\newcounter{mycounter}

%----------------------------------------------------------------------------------------
%TCOLORBOXES
%----------------------------------------------------------------------------------------


\begin{document}


\begin{mybox1}[label=one]{sample}{Gebäudeheizlast nach DIN 12831 nach Temperatur}
This is a \textbf{tcolorbox}.\par
a lot of text here ... This is Example \ref{one}
\tcbsubtitle{\textbf{ Formeln}}
some text
\end{mybox1}

\begin{mybox2}[label=one]{sample}{Gebäudeheizlast nach DIN 12831 nach Temperatur}
This is a \textbf{tcolorbox}.\par
a lot of text here ... This is Example \ref{one}
\tcbsubtitle{\textbf{ Formeln}}
some text
\end{mybox2}

\end{document}