If what you want is to add a mod so it instant fires what you want, you’re gonna need to add the modifier on top of each of the blocks so it always happens.
Example /cast [mod:alt,@mouseover,nochanneling] Life Cocoon; [nochanneling] Touch of Death.
Adding it only to a single block, which is why I assume you say it doesn’t work perfectly, will only fire the mod when the loop is at the block that does fire it.
Visual example: https://imgur.com/a/yWjOPeI