this is a pretty up to date list, although i am not sure this IS honestly the best place to ask. I don't know that the people here do a whole lot of freeform costume design in general since most cosplayers are not doing original designs and many of them aren't 2D artists. i used to be a professional artist and i do a lot of sketching to work through construction problems but i use paper because i'm old. (and because i like paper and my phone is too small to bother drawing on.)
of the ones on that list, I've used the desktop version of artrage and it's pretty good and (important) has layers, which is good for costume design because you can put garments/looks on different layers and remove them, almost like paper dolls, to see what looks the best.
it is possible other people will have more helpful input than i do.