Hello,
Wolfgang helped me to get this:

1.a.
b.
c.
2.a
b.
c.

I have unfortunately lost the code he had proposed to me. I get this:

1.a.
1b
1 C
2.a
2.b
2.c

Thanks
Fabrice

\setupitemgroup
   [itemize][1]
   [color=darkred,
    distance=\spaceamount,
    option={packed,fit,intext,n}]

\setupitemgroup
   [itemize][2]
   [color=darkred,
    distance=\spaceamount,
    option={packed,fit,intext,a}]