You could use a detached title and add it to an enlarged margin:
\documentclass{article}
\usepackage[most]{tcolorbox}
\usepackage{lipsum}
\tcbset{%
enhanced,
coltitle=black,
detach title,
left=10mm,
overlay={
\node[rotate=90, minimum width=1cm, anchor=south,yshift=-0.8cm] at (frame.west) {\tcbtitle};
}
}
\begin{document}
\begin{tcolorbox}[title=test]
\lipsum[1]
\end{tcolorbox}
\end{document}

Or if you prefer a separation line between the title and the text:
\documentclass{article}
\usepackage[most]{tcolorbox}
\usepackage{lipsum}
\newtcolorbox{mybox}[2][]{
enhanced,
coltitle=black,
title={#2},
sidebyside,
detach title,
attach title to upper={\tcblower},
lefthand width=0.3cm,
#1
}
\makeatletter
\renewcommand\tcbtitle{\ifx\tcbtitletext\@empty\else%
\leavevmode{\rotatebox{90}{\color{tcbcol@title}\kvtcb@fonttitle\kvtcb@haligntitle\kvtcb@before@title\tcbtitletext\kvtcb@after@title}}\fi}
\makeatother
\begin{document}
\begin{mybox}{Title}
\lipsum[2]
\end{mybox}
\end{document}
