This mighty table mode is called "natural tables" or "automatic tables". I'd call it "HTML tables", because it's very similar to them. They're especially suited for XML conversions.
Beware: every element must use \b ... \e!
You find a lot of samples in enattab.pdf
\setupTABLE[row][odd][background=color,backgroundcolor=red] \bTABLE[split=yes] \bTR \bTD[nr=3] 1 \eTD \bTD[nc=2] 2/3 \eTD \bTD[nr=3] 4 \eTD \eTR \bTR \bTD 2 \eTD \bTD 3 \eTD \eTR \bTR \bTD 2 \eTD \bTD 3 \eTD \eTR \bTR \bTD[nc=3] 1/2/3 \eTD \bTD 4 \eTD \eTR \bTR \bTD 1 \eTD \bTD 2 \eTD \bTD 3 \eTD \bTD 4 \eTD \eTR \eTABLE
You get automatic page breaking with the option [split=yes].