extracting series in a list

hi everybody

This is my first post on this forum.

i've a problem with a list of curves i would like to slice into x series of curves

i have several lists of 12 curves i would like to slice into 4 lists composed of 3 numbers to loft them separately. The value of 12 is an exemple to simplify my question but this value is not static and can increase to 15,18...
I didn't find a solution to extract my values dynamically, does someone have a solution?

tanks in advance