you can find it in the manual under vars - multidimensional arrays...

I don't think it's too bad. the algorithm is

[number_of_elements_in_a_row*current_row + element_number_in_current_row]

so, if you'd want to sort the rows, you simply have to move
[3*current_row + 0] and [3*current_row + 1] and [3*current_row + 2] in order to move the entire row. It does take some time to get your head around it, I guess, but once you get it it's a great option...