Hello,
How to have :

Démonstration --- 1.one
2.two
3.three

Thanks
Fabrice

\defineenumeration
  [proof]
  [text=Démonstration,
   alternative=serried,
   number=no,
   headcommand=\groupedcommand{}{~---~},
   headstyle=bolditalic,
   %headcommand=\groupedcommand{}{:\,},
   width=broad,
   closesymbol={\symbol[square]}]

\starttext

\startproof
   \startitemize[n]
   \item one
   \item two
   \item three
   \stopitemize
 \stopproof

\stoptext