\documentclass{article}

\usepackage[enable-debug]{expl3}
\ExplSyntaxOn
\debug_on:n { all }
\ExplSyntaxOff

\usepackage[default styles]{mkessler-thmstyle}
\usepackage{mkessler-groupthm}
\usepackage[ ]{verbatim}

\GenerateTheoremVariants
[
  group = {star, dagger},
  thmtools = { style = thmgreenmargin },
  name = Beispiel 
]{example}

\GenerateTheoremVariants
[
  group = {star, dagger},
  thmtools = { style = thmorangemarginandfill }
]{lemma}

\DeclareTheoremVariants{example} { !s !t+ }
{
  \IfBooleanT{#1}
  {
    \AddTheoremToGroup { star }
  }
  \IfBooleanT{#2}
  {
    \AddTheoremToGroup { dagger }
  }
}

\DeclareTheoremVariants{lemma} { !s !t+ }
{
  \IfBooleanT{#1}
  {
    \AddTheoremToGroup { star }
  }
  \IfBooleanT{#2}
  {
    \AddTheoremToGroup { dagger }
  }
}

\begin{document}

\section{a}

\begin{example}
  test
\end{example}

\begin{example}+
  test
\end{example}

\begin{example}*
  test
\end{example}

\section{b}

\begin{example}*+
  test
\end{example}

\begin{example*}
  test
\end{example*}

\begin{lemma}+
 test 
\end{lemma}

\begin{verbatim}
  \NewTheoremGroup[keys]{name}
  \ProvideTheoremGroup
  \RenewTheoremGroup
  \DeclareTheoremGroup

  \AppendToTheoremGroup[keys]{name}[before / after ? ]

  \NewTheoremFamily
  \ProvideTheoremFamily

  \DeclareTheoremFamilyOptions
  \ProvideTheoremFamilyOptions
  \RenewTheoremFamilyOptions
  \NewTheoremFamilyOptions

  \AddTheoremGroupParent{child}{parent}

  \NewTheorem -> starred + unstarred family + options
  \ProvideTheorem

  \NewFancyTheoremFamily[mdframed = , group, name, thmtools, style = ] wrapped \NewTheoremFamily

  \DeclareStandardTheoremFamilyOptions
  \ProvideStandardTheoremFamilyOptions
  \NewStandardTheoremFamilyOptions
  \RenewStandardTheoremFamilyOptions

  \NewFancyTheorem[mdframed =, thmtools = , name = , group = ]{name}

\end{verbatim}

\section{TODO}

\begin{itemize}
  \item style = parsen
\end{itemize}

\begin{verbatim}

\usepackage
[
    big   = { document, section, subsection, no },
    small = { document, section, subsection, no },
    tiny  = { document, section, subsection, no }, 
    notheorems
] { fancythm }



\end{verbatim}
\end{document}