Si, puedes, mas o menos. You have to re-draft it into Seamly2D. Once that’s done properly, it’s a cinch to re-size it however you need, even non-gradable sizes. Thus you can pleasantly eliminate all but one fitting session, & even that one should be more of a formality.
I did come up with a way to enter existing patterns of a known size… which is not drafting using a given pattern system per se, but rather locating the grade points of the pattern pieces. I outlined how I did it with this pattern…