\setupindenting[yes, small]
\setupfloats[before=,after=]
\definedescription
[MyEntry][alternative=serried,width=fit,before=\indentation,indenting=yes]
\unexpanded\def\MyCommand#1#2#3%
{\startMyEntry{\bi#2:}#3\stopMyEntry}
\definesorting[My][Mys]
\starttext
\startcolumnset[TwoColumns]
\definecolumnsethsize{TwoColumns}{1}{1}\One
\startbuffer
\placetable[lrtb][tab:mytable]{My Table}{
\bTABLE[option=stretch,textwidth=\One,align=middle]
\bTR\bTH Foo \eTH\bTH Bar \eTH\eTR
\bTR\bTD Bar \eTD\bTD Foo \eTD\eTR
\bTR\bTD Foo \eTD\bTD Bar \eTD\eTR
\eTABLE}
\stopbuffer
\My[Q]{\input knuth\getbuffer}
\My[R]{\input knuth}
\My[C]{\input knuth}
\My[A]{\input knuth}
\placelistofsorts[My][criterium=all,command=\MyCommand]
\stopcolumnset
\stoptext