I need a list structure that can be numbered in different ways as the
occasion warrants.

In this case, I need:
1. text
2. text
    2.1. text
     2.2. text
          Text
          Text
             A. text
             B. text

The problem seem to be in turning off the cumulation of numbers in the last
entries (fourth level).

\defineitemgroup[MyList]
\setupitemgroup[MyList][1][broad,joinedup,packed,autointro]
[itemalign=flushright,left={},right={},stopper={.},margin=3pc]

\setupitemgroup[MyList][2][broad,joinedup,packed,autointro]
[itemalign=flushright,left={},right={},stopper={.}]

\setupitemgroup[MyList][3][broad,joinedup,packed,autointro]
[itemalign=flushright,left={},right={},stopper={.}]

\setupitemgroup[MyList][4][broad,joinedup,packed,autointro]
[itemalign=flushright,left={},right={},stopper={.}]

\starttext

\startMyList[n,repeat]
  \item First level text
  \item First level text
  \startMyList[n,repeat]
  \item Second level text
  \item Second level text
\startMyList[symbol={}]
  \item Third level text
  \item Third level text
\startMyList[A]                        %<=====
 % \startMyList[A,prefix=no]          %<=====
  \item Fourth level text
  \item Fourth level text
\stopitemize
\stopitemize
\stopitemize
\stopitemize


\stoptext

With \startMyList[A], I get
       2.2.2.A. Fourth level text
       2.2.2.B. Fourth level text
With \startMyList[A,prefix=no], I get

      ▷ Fourth level text
on each line.

Any suggestions or pointers will be gratefully received.

Alan