To save your own label formats, you can edit the file "cmll1601.inf".
Layout of a label definition (all measurements in 1/1000 mm):
<A> <B>, <C> = <D>, <E>, <F>, <G>, <H>, <I>, <J>, <K>
A: code, B: description, C: page size, D: label width, E: label height, F: horizontal distance between labels, G: vertical distance between labels, H: number horizontal, I: number vertical, J: margin left and right, K: margin top and bottom
e.g. 3420 universal labels, 70 x 16.9 mm = 70000, 16900, 0, 0, 3, 17, 0, 4850