Combo for Y is added; Combo for N is kept for compatibility.
Combos for colon, semi-colon, question mark, and double quote are added.
Symbols are re-arranged so that more common symbols for programming are under stronger fingers.
Combos for many symbols are added to Symbols and Parentheticals layers, so that SHIFT is not needed for any symbol.
Numbers and Custom layers are swapped, because numbers are more common, and it is easier to hold down pinky on the lower-row key and press the other keys on either row, than hold down pinky on the upper-row key and press the other keys on lower-row.
Numbers are re-arranged similar to ten-key (1 thru 6).