Hah! Yeah, stretching sprites in a way that doesn't look horrible is a pain. I remember wrestling with literally this problem a while ago, lightning and all. I think there a Line Renderer thing in Unity you can use.
Using gamemaker, though! Which does have a draw_line function, though using draw events at all in GM is wonky and i kinda have bad experiences with it, hahahah
I guess i might need to master them if i want good effects though! god help me (?
Yeah, I remember when I was learning particles in unity most of it was me replacing sprites in preexisting particle effects with random UI elements and textures to get ideas for proper fx, haha.
Are there some FX you could grab in a pack or something to pull apart and see how they work?